Repurpose shoutitis as impitis.

[dck]

Shoutitis isn't a particularly relevant mutation even when you're mostly stabbing or are otherwise depending a lot on stealth because those kinds of characters (the ones that survive anyway) already have to deal with the reality of monsters often noticing them and shouting; what's worse, the chance of it happening in any relevant context is very low, low enough that it doesn't bring anything really new to the table.
What I propose is getting rid of the random shouts when exploring and making it so that the player has a chance of insulting a monster with imp speech as it comes into view. Without much thought put into it 1/30 1/20 1/10 chances for the mutation to go off sound like it would be okay.

[ackack]

That sounds pretty good.

[duvessa]

While this is an improvement over current shoutitis, I feel like it's still awfully similar to just decreasing your stealth.

[Sandman25]

Maybe it should have a very small chance to cause confusion/fear: a sudden shout can scare sometimes. Though that would be a double-edged mutation then.

[Roderic]

Tourette syndrome in Crawl, omg

[Igxfl]

What about a small chance that your insults zerk monsters? That would make it different from a boring stealth penalty.

[Curio]

What about a small chance that your insults zerk monsters? That would make it different from a boring stealth penalty.

Appears in LOS. Zerks. Being kited until wears off. Killed off being slowed.

[dck]

Monster berserk doesn't really work like that.
Berserking enemies you taunt sounds cool on paper, but I think the chance would probably have to be sizable for it to be not just another obscure thing that never happens in practice and you don't know about if you don't check the source. That said, there are still problems with berserking enemies like that. Mostly things like in practice you can just pull a rupert and block enemies that berserk and have no means to become adjacent to you with other less dangerous (and less berserk) enemies.
These are basically the reasons shouting at enemies making them berserk is something I initially considered and then discarded.

[sgrunt]

Sorry, no demon taunts yet. Maybe that's next.

[dck]

Working on mostinsultingpatch as we speak GRUNT.

[gammafunk]

I still say it's terrible that Grunt did dck's homework. The child will never be independent unless he learns to do things on his own!

[dck]

gfunk clearly can't handle dat 28 cha.

[TheArcanist]

While this is an improvement over current shoutitis, I feel like it's still awfully similar to just decreasing your stealth.

As much as I find this proposal amusing, I have to agree with this. So long as the mutation is governed by random chance, there isn't much of a practical difference between a monster waking up/noticing you from the mutation triggering and a monster waking up/noticing you through a failed stealth roll other than a line of randomly-generated dialogue in the message box.

To that end, we should probably just bite the bullet and just remake shoutitis into a minus stealth mutation, possibly flavored as the player character compulsively muttering and cursing under their breath.

[Sar]

but that's less funny than random cursing