I won’t say the obvious one where they move in front of you when you’re trying to path/terraform. Cast master is one of them, I’ve done it before but it’s such a pain to do. I remember when I did it during easter and the eggs interrupt fishing but don’t count as a fish so I did it on hard mode.
Making an island then months down the line finding you have a super awkward placement of the airport/town hall with the design you want but don’t want to restart.
At least on the bright side, at least villagers don’t move into random locations anymore. They actually used to appear absolutely anywhere 
so you could have a gold roses flower patch and their house would spawn ON it destroying everything