The only reason I could think of for why we don't let everyone who commented on a post add their tags is that this is how AC is checked. But as is mentioned above, you can easily check any journal's posts with the /?poster=username code... though this doesn't take into account when people use loss-specific journals -- but I guess that's a simple enough correction to make when AC goes up anyway.

So yeah, basically I'm in favor of it :V