Yeah, it must seem a little weird
If a mod deletes your post and half of it was on topic, they should of just edited it instead. In some cases, they should PM you. But I've gotten some of my posts deleted and they were off topic, and I felt sort-of strange about it, but I feel like if the whole post is off-topic then maybe it should be deleted!
So I don't get many posts deleted because I try to stay on topic. That's where the problem is - and if it keeps happening, then I think you should consider changing the content of your posts.