Particularly old posts. For example, post #958273 is locked despite there never having been any dispute over its rating.

Searching the moderation log suggests that no rating locks have been applied since before the site rewrite, which comes across as very suspicious to me - I wonder if it's another case of forum #306626?

I used to do it just for the heck of it. Now I don't care.

wat8548 said:
Searching the moderation log suggests that no rating locks have been applied since before the site rewrite, which comes across as very suspicious to me - I wonder if it's another case of forum #306626?

Yeah that looks like some sort of bug where it's not being recorded or something. I just locked the rating of post #2896117 as a test and I can't see any logs of me locking it anywhere.

All the history sections come up blank except the Tags/Desc which has the initial upload.

wat8548 said:
Particularly old posts. For example, post #958273 is locked despite there never having been any dispute over its rating.

To pre-emptively stop rating vandalism. There's no reason not to lock blatantly explicit posts. At one point, all scat etc posts were locked, but I don't think anyone's kept up with the new posts.
It's also helpful for new users, in cases such as bare breasts. When someone new tries to set the rating to E and finds out that they can't, that might clue them in to the fact that it shouldn't be rated E.

For users of sufficient rank, locking is an option during upload, and it's heavily recommended that you use it. (That type of locking doesn't get recorded anywhere, afaik.)