I'm had at least 4 or 5 people (that I know of) who've used my character sheet formating and rule sections nearly word for word. I don't really mind, it's kind of flattering in a backhanded sense. Usually people ask if it's okay, I always say yes. I just ask people consider crediting me for the formatting so if on the off chance they come across my game, they know nobody is ripping on another off, and I won't lie, I enjoy being acknowledged for the work I put in even if it's for something inconsequential.

To me, it's like a group project in school. It's irritating when you put in all the work while your partner gets credit for it.

Does it matter in the grand scheme of things? Of course not. You should still do the polite thing and ask if you can borrow ideas or formatting. I mean, unless someone rips one of my characters or plots, I'm not going to bug them about it or anything. This is a hobby, not a livelihood.