Why would he decide to post ''nour''

To bait people like you in believing that satoshi is back (which is unlikely at this point).

Also another question he added a new friend after a long while, does it make any sense?

It doesn't, maybe it's the hacker's account.

It seems to me that it was a real Satoshi and he showed that everything still exists. most likely this post had some meaning

Yeah it was real just like the post that was made during 2014.