As a perm-account holder, I can see up to 100 most recent comments I posted (anywhere) and received (@ my LJ). I thought there also used to be a similar replies-to-me-anywhere-on-LJ feature, which was useful for keeping track of community conversations, but I can't find it anymore and may be making it up altogether.

And I see what you mean about Pillowfort it being part of user culture. It's an interesting idea which could be handy! (depending on how people use it, of course, like anything)