When I first started using uEmacs, one of the most confusing things was the fact that the adaptation had not been entirely completed, or at least on my platform (an Atari ST), the keyboard mappings were not entirely idiomatic—they hadn't kept up with the differences between VT-100-style keyboards and, well, everything else.
I think this explains why I got very habituated to the alphabetic keys for deleting stuff, but don't have the non-alphabetic keys as deeply ingrained.
So, while C-d (delete-char) for deleting the next character is
definitely embedded in my fingers, and I use C-k (kill-line) like an
old friend, and even M-d (kill-word), I still have to think hard
before using M-DEL (backward-kill-word)—to the extent that I am far
more likely to do M-b to move back and then do M-d to delete the
words I just backed up over.
So I'm trying hard to get used to using M-DEL (which is Alt-Delete
on most PC-flavored keyboards), because it is actually a fairly common
operation, and I want to be more fluid with it.