There are a bunch of different things that could be going wrong on you site, and helping you is going to be a game of whack a mole for the rest of us.
My suggestion to you would be to revert a lot of the site settings that you’ve changed back to the default and see how things go. For most communities the defaults are perfectly fine and you don’t need to change them.
If you find that in your particular case you need to make some changes, for example to prevent spammers from signing up and posting, I wouldn’t change too many settings at a time to make troubleshooting any problems that come up easier for yourself.
I agree many site setting descriptions are confusing and can be improved. We welcome concrete suggestions of better words, especially from people who don’t speak English as their first language and are confused by double negatives, peculiar english phrases, and so on.
@simon we tried fixing the descriptions in some places, like personal message enabled groups.
Allow users in these groups to CREATE personal messages. IMPORTANT: 1) all users can REPLY to messages. 2) Admins and mods can CREATE messages to any user. 3) Trust level groups include higher levels; choose trust_level_1 to allow TL1, TL2, TL3, TL4 but not allow TL0. 4) Group interaction settings override this setting for messaging specific groups.
If we did this everywhere it would add tremendously to the copy, and add to the feeling that discourse is overly complex. Maybe the answer here is to add a validation so that you can only add one trust level. If you try to add more than one, it will pop up a warning explain how trust levels and permissions work.