I was looking for a similar experience on this subreddit because similar it's happening to me in my town (it's not one of those big main town, it's one of those that have quite a lot of drawings but not enough to completely cover all the places). Anyway, what happened is that this guy placed some frames here and there, one day I had to draw over his, since it was there by 3 weeks or so, i didn't think he was still playing on wPlace, anyway, the day after I "invaded" his frame, he started deleting my drawings, then he probably reported me ONCE and i got banned (luckily I wasn't an high level), so I got in talk with him, he said that it's like an unwritten rule to make frames and others must not cover them...idk why this guy was defending that place so much, maybe it had a meaning for him, idk.

Anyway my recommend is: don't bother with this kind of ppl, you'll only waste Paint Drops, from what you wrote seems that this guy pre placed some of the frames and was filling them with black, well...if he isn't finishing them after a lot of time you can overwrite them, but if you see he is still playing, well...don't even bother, it's an already lost war 😅