My Partner Keeps Liking Their Ex’s Posts

I don’t know if I’m being insecure or if this is actually weird.

My partner keeps liking their ex’s pictures and posts. Not every single one, but enough that I’ve noticed.

They don’t comment or message them as far as I know, but it still bothers me because they act like it’s nothing.

I haven’t said anything yet because I don’t want to seem jealous or controlling.

Would this bother you, or am I overthinking it?