This is something I would like to remain visible, at least for admins (if it is hidden for everyone else, then I guess that is fine), because it really helps me gauge how new a player is when I don't recognize their handle too well. Is this a player who has been here longer but is just coming back? Is this the first or second post of the player? And so on.
I don't base my decisions on what to include or whatever on this at all, but I do shift my tone slightly with this sort of thing -- and if someone has not posted for a while and comes back, that tends to flag me to go see what it was we were last talking about just to remind myself.