As a concept maybe but unless it was done in a way that's similar to say Deviantart's journals or posts on Ko-fi it's not something I can see getting into.
It's also worth considering some folks also already have series on the main site that serve this kind of function so I'm not sure if journal threads would work as well. I mean yes people could respond or interact in relation to what a person is sharing in their respective thread but there's already existing threads for some of the things you've mentioned like "post the last thing you drew", "the watercooler", "post your latest wip" and so on. If anything I worry like it'd end up in the same vein as the intro|feedback|shoutout|category.
To see increased activity or maybe more conversation in those threads would be nice but I think it's a matter of people having the time or being willing/wanting to participate and interact