It's not considered for advertising really.
For example "Come join us on nekki*****.com" would be considered for advertisement.
When you see someone advertise him, a thing you could do is ask him nicely to stop.
If he continues to repeat the server over and over, take screenshot of everything (the conversation and the verbal warning you gave him to stop mentioning other server names) and report the user.
I will not take any actions since his record is clean but however, the user will be verbally warned not to mention other servers.
Thanks for reporting.
