I find that when I tell people "you are welcome" in online forums where I have a reputation as someone who is knowledgeable, it reinforces the idea that 'some folks here know stuff and the rest are losers and are just here to ask questions and beg for help'. I have actively combated that tendency for years in online forums I have belonged to. I have found that "no problem" or "no big" or a similar response fosters more equitable conversation, where more members feel able to be contributing members who know stuff and can give information. Saying "You are welcome" reinforces the idea that what I have shared is "advice" rather than "information" and suggests I have some authority to tell them how to live their lives, which is generally something I do not want. In my experience, it creates a great many problems (edit: including people vociferously attacking me and trying to tear down my supposed "authority", which I never wanted in the first place). Sharing anecdotes, telling my story, sharing information -- this is something any member can do for the benefit of the group as a whole without needing to be "right" or "authoritative" and it undermines the tendency to fight for pecking order which typically goes on.