I'm using FF (v 100, fully updated).
It only seems to be happening in posts where I had a Fieldset, then removed it. Even when I put it back, the issue still remains. I've been trying to put together some basic templates that I can copy/paste on various threads...not having much luck. This interface is exceedingly frustrating.
Thanks as well for the info on spoilers. Having to brute force a spoiler with a table is ridiculous. That's absolutely asinine, and HORRIBLE code, but if that's the only way it's going to work, I guess I'll have to learn to put up with it.