I can't reproduce the "+2" bug with the real-time game multiplayer template. I managed to become host with the name "y", which is a single character, proving that the multiplayer engine supports hosts with a single character name without adding "2". The most likely cause is the name was already taken, which is more likely with single character names since there are fewer options.
If nobody can connect to you, it suggests your NAT is blocking inbound connections. This is not a Construct 2 bug. It's to do with the architecture of the internet. The first multiplayer tutorial covers this in part.
Closing as I don't see any evidence of Construct 2 bugs here; most likely you are just confusing various issues of Internet architecture, server name assignment, and perhaps muddling your events with displaying player aliases. In order to investigate bugs we need clear unequivocal proof that the problem is in Construct 2 and not a mistake in your events.