If they're sharing the joy of discovery that's great. Lots of people though are gloating. "Haha, you're stupid, you didn't know X and I did". In other words, they're the ones not being charitable by assuming you don't already know X.
Trying to think of an example it usually goes something like
A: We should do X
B: No. See this document (the sharing part)
A: I wrote that document and I'm telling you we should do X (the "I already knew this" part)
Trying to think of an example it usually goes something like
A: We should do X
B: No. See this document (the sharing part)
A: I wrote that document and I'm telling you we should do X (the "I already knew this" part)