Well, I have that happen in my game. I have the communitylotskiling hack, and after my sims visit the gym when I'm playing another household and visiting the same gym, once I get to the household in question and my sims eat, they will stand up and do the "Oh I'm fit now' gesture. Its because this gesture can't be done on a community lot.

Although I do have community lot skilling, in this case I don't think it's that. With the current machine I'm using to run the game, load times for lots are fairly long, like five minutes or so, so I'm not really using community lots on it. The Sims in question haven't recently done any activities that increase fitness, either. No swimming, no jump-roping, no exercise machines, no TV/radio working out, no bouncing on Nix's Sim Bouncer, no nothing. Just salmon-eating.

...I wonder if having learned Physiology might have something to do with it. I can't recall if the Sims in question have done that...

Yes, both of those should be completely safe. I assume that you added a community phone and garbage and removed the residential mailbox and garbage?

Yes on adding the community phone and garbage, no on deleting the residential items because I thought that was a game-killer. Do I just use moveobjects on to remove them?

As far as I know, there's no harm in leaving them, except that you might get bills delivered to the community lot.

No, it won't kill your game to remove them from a community lot. It's a bad idea to remove them from a residential lot, because their lack will affect the gameplay when the lot is occupied.

Yes, you can just use the moveobjects cheat.

Thank you for the advice and clarification! The residential items are mildly aesthetically displeasing, but I was willing to put up with aesthetics for a stable game. But now I don't have to choose!