I think the problem is that acronym is not about reading silently but 
reading aloud.

So if you said
  EksEmEl
i.e. spelling out each letter then you are using an abbreviation.

But if you said
   Eksml
i.e. pronouncing it as a word then you are using it more as an acrostic. 
However, a really unsuccessful one in English at least, because the ksml 
combination is not idiomatic in English and certainly not euphonious: we 
don't see towns like Axmill or Pigsmill AFAIK.

Similarly, CEO if pronounced by spelling out each letter see-ee-oh is an 
abbreviation, but if you attempt to read it as a word,  see-oh, it is an 
acronym too. (I don't know that anyone does that.)

So I think it is futile to discern acronymicity from merely looking at 
the letters: it is how they get read that is the determining factor. So 
RADAR and LASER are definitely acronyms because we conventionally read 
them aloud as words perfectly easily.

So my vote is that XML is not an acronym, and that this can be 
empirically tested by observing whether guinea pigs read out each letter 
or try to make a continuous sound with it.

Cheers
Rick Jelliffe