I've been hesitating about suggesting this because I wasn't too sure how well the idea would be greeted. This is a case of "want" rather than necessity, so I suppose I'm bringing this up to see if it's wanted and if it's a possible update in Danbooru's future.
Basically the idea is that Danbooru would have a sort of (mutual) friend system that would make it so you could keep track of said friend's posts without adding user:Example to your subscriptions. Alternatively, it could be a function that allows one to subscribe to another user's posts rather than a more complicated friending system. The posts from these subscriptions wouldn't show up on your profile, but rather they'd be under a tab much like Popular posts/etc.
You could always just add user tags to your subscriptions like I mentioned above, but then content of theirs that you may not like or be interested in is going to show up on your profile and hide other things that you'd prefer. (I tried to overcome this by making a seperate subscription for users alone but the tag format seems to break it.)
It could also tie into having names for easy access in dmail somehow if that wouldn't be too complicated.
Anyway, I do realize this is a bit over the top and I'm not quite sure about all the details myself, but maybe if others like the basis of the idea they can contribute and we can get something going here.
With that, hurr, go wild.
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