Platform definitely has an effect on how people act. I have little to no presence on FB and twitter while my Tumblr presence is active, but in a passive kind of way (I have meaningful interaction with literally no one).

Being on DW is actually kind of nice! It encourages interaction the kind of which I haven't really been involved in since I was active on FF.net back in the day (I never actually figured out LJ before the purge, lmao).

As to keeping fandom and real life separate; it feels a lot like a one way street. If I'm open about fandom with someone online I'm pretty open about RL stuff, but I absolutely don't mention fandom stuff around people IRL unless they let something slip. I was teased about fandom stuff pretty harshly in middle school so I literally never bring it up unless someone else does first.