So hypothetically: Make 'who + letter' the only syntax for 'who', so only letter searches can be made.
It would basically be an anti-feature and make it harder to check who is on the network, and I understand if everyone would hate it. But I think it could have a few advantages in terms of reducing small-worlding and making it much more difficult to suss out if a character is awake at particular times, or whether groups of characters are all awake together or not, or to get tipped off that some super dangerous/famous character is active.
Also ctags are pretty much the strongest advertising that exists in-game, since they're constantly seen over and over for free, and not being able to rely on slapping the job in the tag and having every PC know, might drive more SICAD or business card use.