Berendol mentioned that this may actually exist in recent versions of Angband. The idea is to collapse repeated messages in the mirror window.
So, the messages:
You miss the giant louse, you wretched wuss!
You miss the giant louse, you wretched wuss!
You miss the giant louse, you wretched wuss!
You miss the giant louse, you wretched wuss!
Would become:
You miss giant louse, you wretched wuss! (x4)
This would help alleviate the problem of multi-swing fights resulting in wodges of text blasting through the mirror window, which can make it difficult to use.
-Fink