Re: choosing congregations: I think you’re right; there may certainly be sad cases where you cannot find a good congregation for the belief system that fits you best, and a good congregation is really necessary. But again, I think this is a place where Seeker and Spirit need to have some give and take. It may be the case that in this single life, it is part of the Seeker’s journey to walk a difficult path alone. It is a worthwhile thing to learn…

“If there were no sense of community there, or an unhealthy one, it would be bad to join, no matter what their beliefs are. (You could still adopt the philosophy, though.)”

This may cause problems if a core element of “the philosophy”/the beliefs involves (or otherwise requires) place very high importance on joining and functioning within a community/congregation: the philosophy/beliefs may focus on/”live themselves through” participation in group events, and may even strongly prohibit “going it alone.”

For example — from what I know of Mormonism, a faith I believe you’ve had some contact with — a person who converted to (or grew up in) Mormonism, but who could not or (even for some strong/compelling reason) did not meet with other Mormons for worship or other purposes, would have effectively “zilch” Mormon life. (His/her “solo” version of Mormonism might somewhat resemble joining a football team, never attending practices or games, but working out alone in one’s room with a football and calling this “solo football.”)

Re the very important distinction between joining a belief-system and joining a congregation — C. S. Lewis’ SCREWTAPE LETTERS have some (in my opinion) very interesting and thought-provoking things to say about the difference and why it matters.
As you recall: early in Screwtape Letter Sixteen, we see the professional soul-warper Screwtape advising his younger colleague Wormwood about how to make sure that the soul in Wormwood’s charge does *not* stand the least chance of learning anything true or important from the church he attends. Here, Screwtape considers it of prime importance (for successful soul-warping) to encourage his victim to go “congregation shopping” as we might say, in order to find a congregation that perfectly fits, that perfectly pleases, but that (by the same token) does not in any way challenge his present self.

Screwtape advisest that, if the soul-warper can’t cure a churchgoer of looking for God, then “the next best thing is to send him all over the neighbourhood looking for the church that ’suits’ him until he becomes a taster or connoisseur of churches. … The congregational principle
[of joining a congregation
because you like the congregation,
rather than the "parochial principle"
which Lewis favored -- joining a church,
finding a nearby congregation of that church
and sticking to it ]
makes each church into a kind of club, and finally, if all goes well, into a coterie or faction … [and] makes the man a critic where the Enemy
[the enemy of soul-warping:
God, or Spirit as you would say]
wants him to be a pupil.”

Further down in the same Letter, ofof course, Lewis *does* address the fact that “congregation shopping” (instead of just sticking with whatever you can find nearby) may become necessary even though Lewis plainly doesn’t like the necessity:
Screwtape notes to Wormwood that, of the two churches nearest Wormwood’s current victim, the first has a cleric who sees his job as protecting the congregation from all inconvenient truths, and the second has a cleric who runs his church on hate, often preaching “some kind of theocratic Fascism.”

(One could even go further: I suspect that Lewis would have heartily approved a bit of “congregation shopping” if the pulpits of nearby churches proved to house thieves, terrorists, or child-molesters.)

“The stories you tell of people ignoring and/or underestimating the handicapped totally amaze me. I don’t understand how anyone could reach adulthood and still act that way. Heck, children usually don’t act that badly.”

A partial answer: I have seen adults *train* their children to “act that badly” towards the handicapped: just as part of enculturating the next generation, I suppose.
Typical instance –

The scene: a bus stop. A woman in a wheelchair (who has in her lap a cat-carry box with a cat inside) sits near another woman who has a small child.

CHILD [pointing to wheelchair-using cat-owner]: Mommy, that lady has a kitty! Can I ask her if I can pet it?

MOM: No, honey … she’s a wheelchair person. Remember, she probably isn’t able to see, hear, or think like we do.

CAT OWNER IN WHEELCHAIR [gesturing at the cat and ignoring the mom's stupid remarks]: Oh, you want to see Snowface? If your mom says “Yes,” you can come pet him through the holes [in the cat-carrier].

CHILD: The kitty lady said I can pet her kitty! Can I? He’s so cute!

MOM: I told you, we don’t bother wheelchair people. If you want to pet the wheelchair lady’s kitty, you’ll need to ask somebody next to the wheelchair lady. How many times have I told you it’s not nice to talk to wheelchair people?

CHILD: Oh, sorry, I forgot. [Turning away from the cat owner, to a man sitting near the cat owner]. Mister, can I pet the wheelchair lady’s kitty?

MAN : [just shrugs -- child goes over and pets the cat, without a word to the cat owner. Child returns to mother]

MOTHER [smiling] That’s right. It’s good to be nice to wheelchair people.

Having seen things like this, I certainly will read MOVING PICTURES and get to know Gaspode and his similar experiences.

Re:

“As for the question at the end of your penultimate comment: this is the great question of religion, isn’t it? How did Moses and Abraham know that they really heard the voice of the Lord? (That burning bush could have been a hallucination, too.)”

Yes — and, just as obviously, Abraham could have hallucinated a divine voice telling him to kill and roast his favorite son: today, we call the hearers of such voices “psycho serial killers” instead of “great religious leaders” (And I’d really like to know what Abraham’s neighbors called Abraham, after word of the event got out … the Bible doesn’t say: but — as you probably know — many rabbis figure that, by attempting human sacrifice, Abraham actually *failed* God’s test instead of passing it.)

Whatever standard can discern between “inner voice worth following” and “inner voice NOT worth following,” a big part of that standard presumably must involve /1/ “what happens when you follow this inner voice?”, /2/ “does this inner voice conflict with other known/demonstrably valid-and-important information?”, and /3/ “does this voice tell me verifiable facts that I didn’t already know, useful ideas I couldn’t have come up with, etc. — or does it just confirm what I already believed or what I would already want to believe?
(For example: suppose that a person with severe diabetes — who misses fudge and ice cream — hears a “divine voice” commanding: “Throw away your insulin, and eat fudge and ice cream three times a day: make sure you eat only the kind made with real sugar.” The recipient of this particular message would have excellent reason to attribute it to no other source but his/her own craving.)

Re:

“How do you know that everything you see and hear isn’t the product of your imagination? Maybe all of your reality is just a projection of your brain in some way. Logically, is there any way to argue against it?”

I see only one way out — a way that others have seen too:
if we assume that everything I call reality merely originates within my brain (as a sort of very complex, very convincing hallucination, then at least that proves the existence of my brain (or of whatever else the hallucination originates within. Conceivably, what I regard as “my brain” — even my entire self and all its perceptions of the world — might in fact exist only as an artificial-intelligence software subroutine on some computer somewhere … in which case, the software and the computer at least would exist. If so, I would rather find out the facts than continue to dwell within the hallucination.)