OP - Original Poster
OP: Original Poster (like you explained) or Original Post.
OP can be used like two words: Topic and Thread. Many posters don't know difference between Topic and Thread as well as they can differentiate what OP implies for either Original Poster or Original Post. It must be taken in to a specific context.
OP, what is it?Terminology'OP'
Original Post / Original Poster. This could refer to either the user that started the thread or the first post in the thread. If you are in the hardware section then it could also mean 'Over Power'.
There are real people using OP instead of thread? It must be some beginners, no? But for topic I agree with you, many people are using it as synonym of thread including me while it's not. It's the subject of the thread, the "Original Post" normally.