Lol its kinda annoying to me..im like give people time to answer!
Good question.. I had that response today on something I posted and I was like.... Bump... hm ok.. good advice.. NEXT.... LOL ... I didn't know either..
They are trying to get it to the top of the feed list. I think everytime someone comments it goes to the top so more people will see it. If nobody responds you can "bump" it up. A lot of times someone else will be wondering the same thing and bump it to get someone else to answer.