/seen only tells you the last time a player was on a specific server. No other information is given out from that specific command.
I typed in the command "/seen PandaBear__" and that was all I got. I believe you might be thinking of the command /whois where it tells you info about a certain player. Also, if you're scared of someone getting your IP through in-game commands, you shouldn't worry too much. (I'm not 100% certain on this please do not hold this against me in the future) If I'm correct MV uses BungeeCord. I also have used BungeeCord for a network of servers. With my experience, Bungee connected every player onto one IP as soon as they join the hub. Therefore, all players would have the same IP. So if I did a command such as /whois, everyone would show up with the same IP. I could be wrong but I know for sure /seen does not give out your IP
Well what server are you doing this on... I am currently using a host. But I'll be sure to try bungeecord on my server.
Mineverse's DDOS protection blocks IP addresses to be visable when /seen is used. Nothing you need to worry about, people can't see your IP.