It's marked by the sv_tags system.
Which is only useful when joining random servers from the in-game server browser, not the global one, not to mention the favorites section... Are you afraid that people might not join the server if it was properly marked as a nocrit server?
Well - at least that would say something about the popularity of this concept and probably fill the other servers quicker (e.g. the UK one :-P). Otherwise I feel as if we cheated people into joining this custom server to a certain extent, especially since no critical hits aren't readily apparent like ETMI observed.
We can't wonder that Valve is undertaking more and more drastic measures against gameplay altering servers then...
Might I ask what the motivation behind not modifying the server name is? You surely have given it some thought, Saint, because we had properly tagged servers before and there has to be a reason for this change.
I think it would only be fair to everybody, both the people who like criticals and ones who don't, if we informed them upfront what type of game they are about to join - that way the nocrit aficionados could flock to Server #3 and the others to Servers #1,2,4 without ever wondering what the hell is happening. ;-)
You know - Server #4 is "tagged" as a UK server in the name and following your logic it wouldn't need to be - why should people know about that if they can simply look at the ping column and realize that it is in a different country than the rest...
P.S. Aren't ALL of our servers tagged anyways because of the increased player counts (and some minor spawn time alterations if I'm not mistaken)? This only adds to the confusion since you need to really investigate the tags to realize what kind of server you're dealing with.
Update: Yeah, I checked and our servers are indeed all tagged - the info about their peculiarities gets lost in all of them, especially since they don't even fit in the "tags" row. Nocrits is nocrtis but the server also runs with disabled damage spread and together they alter the usual FFA gameplay quite a bit, changing it more to a clan-war type experience (which is what the proponents of the server wanted to achieve after all).