I dont disagree that depressive online spaces breed more depressive cycles, but good lord, what you seem to be implying is even worse. You can’t just brute force “hey cheer up” no matter the group structure.
like particularly this:
> If that clue isn't heeded the friend often gets targeted 1:1 offers for help and can eventually just be shut out of the group altogether for being too negative.
Is not ever helping a clinically depressed person. especially when offers of “help” are often quite victim blamey and threatening like the tone of your post here - stop bringing the vibe down, or we’ll make you feel even more isolated! good lord. Try bringing them a meal or giving them a compliment first? holy shit.
I could give you a detailed response but, given your tone, instead I'll say: assume the best and don't make everything about yourself. Several people I know have struggled with negative mental health effects of finding themselves in a caretaker role for a mentally ill friend or partner. In my experience offline groups (not individual relationships) have pretty good immune systems for this. They also often do band together to support or help a struggling friend.
In the same way that you expect a depressed person to receive charity, please offer it in your responses.