Hello!
After merging layers togerther (with layer below) the "merged" writing appears on this merged layer.
I hate that, I know it's merged, cause I just did that! And every time I have to manually remove it, because I like to have names of my layers clean and consistent.
Is there a way to turn this off, so this "merged" doesn't appear automatically?

*I think it's "merged" in English, I have Krita in Polish, so if I'm wrong, correct me

I don't think you can turn it off.
With version 4.3.0, that only happens if you merge a group. For ungrouped layers, the merged layer has the name of the lower layer
For grouped layers, the word 'Merged' is added after the group layer name and so it's not really intrusive.
Many people would think that it's a helpful reminder in case you forget where the group has gone.

No, it cannot be turned off, and I doubt we'll make an option for that, it's just too small a thing to add an option for and maintain that.