A lot of people do the only problem are the ones who know very little but try to sound like they know more and can't admit when they're wrong.

I do that sometimes, but I try to not be as stubborn about it anymore and admit politely when I'm wrong

I agree with aeacus. As long as you know what you are talking about, it all good. Its the people who don't know anything about a subject trying to sound like experts thats irritating.

I do this all the time, normally all that I do when on the site. Most of the stuff I comment about is history stuff, as that's what I know significantly more than any other subject.