I think knowing too much, knowing too little, and knowing nothing can all harm you and make you look stupid if you overact to hide or to act as if you are better than who you already are at the stage.
Knowing nothing: It's best to keep quiet, observe the things being said and words being exchanged by actually participating parties who also know what's going on. Then do some research on your own and if you're sure, then jump in the conversion and share only what you've learned. That'll keep the person respected or no change in credibility. If you Keep going without actual further knowledge, but just for the sake of arguing, then it'll sound stupid.
Knowing little: The same goes for this as Knowing nothing. If you speak of what you have learned no harm to you (or even no harm to the listener, the person who may be following your advice or tips!). But if you go too far, far from what your knowledge truly holds, then you'll sound stupid sooner of later when someone with real knowledge on the subject come by.
Knowing too much: This is not bad but can also make a person look and sound stupid. Especially in the case of the minds rushing to let a person know that he/she is wrong. The actual know-it-all will respond by rush arranging the words (may it be in speaking or typing online), leaving some info or backup sources out, where the actual words coming out sound less credible than a know little would say. It is best to give time to listen to others and respond as well, or you'll look stupid with your answers.
I think it's the way a person reacts or jump into a bubble/conversations that make them look stupid.
And if this whole thing will somehow become targeted towards me, I only say random stuffs or advices (stupid or not) for the love of TFS-ers! so shuuush j/k