@Simmer1304hI figured out what it was since I ran into this exact issue in the last few days. I went through the whole thing, even with a fresh install! I initially did some research on this and there wasn't anything I could find when this problem was described years ago, but now I know.
It turned out that the gallery window (news column) was the culprit. Oddly, getting rid of my mods worked in part too, but deleting CC wouldn't be ideal for me, let alone the fact I couldn't pinpoint which one it was (not to mention it still happens whether mods are enabled or not). It didn't look like my mods were actually the problem.
Somehow, of all the people you're subscribed to, and all your own content you save, is tied to the notifications list. So, none of the people replying to you know what you're talking about because there's no trash bin icon to get rid of them. You have to [x] out each one of those things individually, as it's not actually a part of the logged notification bar (there isn't one on the main menu). It's rather convoluted, and the error message is misleading. This doesn't help the social aspect of the game, because I can see one running into this problem for a long time unless they change it.