[BlackFingolfin]

I think you still missed the point: If he is there every now and then, then he still has missed all the water cooler discussions that happened while he was not there. It's not as if they will see him and say "ah, right, now that I see you, we discussed this and this last week when you are not here.".

The only way to fix this is with some concious effort to reproduce the results of water cooler discussions explictly -- and if you spend that effort anyway, you might just as well do it via Skype or Slack... He doesn't have to be on-site.

[kartickv]

It's not all or nothing. If he shows up every once in a while, he's better connected than if he never showed up. People tend to forget people who they don't see.