Is it allowed...

I suppose that's ok. I think

That's your business if you friend someone and talk to them or not. It has nothing to do with the way the website works or the rules involving it because it's not on the website itself.

Sure but its creepy.

Your account on Steamgifts doesn't moderated outside of it. So you can do whatever you want if it's not a post on forum or comment for giveaway. Go ahead and ask him, you won't be suspended.