Yes, I do believe you can become over analytical and give people too much credit. And not just from forums, but from books, videos, coaching, and any other means we use to study and improve our game.
When you decide to study and take advantage of all the resources available to players who truly want to learn and improve, it can be easy to assume that everyone you're playing with is doing the same. When in reality, the vast majority of players are recreational players (even the "regular" recreational players) who never think beyond their cards, or at best, their image of you. They're seldom level 2 or 3 thinkers, so if you're not careful it can be easy to level yourself.
It's happened to me. When I first started studying and understanding poker strategy
beyond the most basic level, I just assumed others were as interested in improving their game as I was, and must be reading all the same books and forums that I was. I'd wind up out-thinking myself while trying to out-think them. Once I realized that and went back to assuming every player is bad until I know different, I saw immediate improvement in my results.