One culprit is:
ItemPreview.
Or more specifically: Rhyono's version. It still had the bug in it.
I would like to keep using Rhyono's version because it still allows me to preview things from my bags, but this menu entry thing sucks.
Another culprit is:
Undaunted Pledges Utilities.
After disabling those two addons, my drop-down chat-menu is back to how it should be:
I've posted comments on both addons' pages.