It's a bit hard to articulate. A few times I've felt really alone, existential type, and I couldn't get myself to open up with friends/family/partner, I would hop on those random global conversation sites. Someone anonymous just being there for me. Kind, gentle, supportive, validating connection. Then when it's time to disconnect, I feel overwhelming sadness... I mean I shared things I haven't shared with my closest friends or family. The permanent loss I feel is intense. Like I'm losing a part of myself.
The weird part is sometimes I'll get their contact info, but by the next day... The thought of contacting them is deeply unpleasant, and I could never have a second conversation knowing they know those parts of me. Yet even though I know I won't ever want to have a second conversation, I still feel that grief of loss whenever I'm in that situation again.
It's on my mind because I read a novel about a woman who everyone forgets as soon as they turn/walk away from her. Over the years, she feels that her existence is meaningless, that if she doesn't have an ongoing connection with anyone, it's as if she doesn't exist...
So you are a lot of yourself with a stranger who then suddenly becomes much less of a stranger which is both a gentle, supportive connection, painful to lose and a suddenly frightening person to reconnect with.
It sounds like you may be tempted to overstep your own boundaries. I have done this in other ways and for me it helps to be kinder and patient with myself and take things slowly. In some ways it can be okay in smaller doses providing one is okay with both the loss and regain of the connection.