It's because the (more) prompt has been changed (atleast the default). You need to press control+k twice (or three times depending on your preference) to not disable more prompt during monster actions.

I don't understand how this change made it through and there hasn't been more complains about it.

edit: if you miss an important message during combat the only way you can check it is by going through the message log. This happens a lot. I guess this change was made because the creator thought that it shouldn't be necessary to check the combat log during combat. This may be true for some characters and more so if you play casually in TILES MODE (visual health bars etc). However, in my opinion many messages are absolutely vital information, especially in ASCII mode (which I use and will continue to use).

I always use Ctrl-k to change it back to the old way, I'd definitely support making the old way the default again.

Especially because what tends to get cut off is the most useful information. E.g., I tried mighty blow against a monster. The result of my attack is gone, I just see all the monster attacks. I think my attack is the relevant one there (or critical hits from monsters)

It feels like what I really want is a "smart" display that, if the buffer is too long, causes all "the <foo> missed you" and "you deflect the foo" to be skipped (but still in the message buffer). I only need to see hits and my attacks.

What we really need is a way to permanently save the Ctrl+k setting in NotEYE to remember our preferences across-characters, so that this becomes a non-issue while it's still being tinkered with and improved.
(Ditto things like HUD etcetera as stated elsewhere.)
I'd support making the old version the default as well, but giving everyone the chance to perm their own defaults is probably best.