My final answer:
In Roman, 4 is IV.
But rot13(IV) is VI!
VI in Roman is 6,
In Roman, 10 is X.
But rot13(X) is K.
K isn’t roman for 1000, but it does mean 1000.
Attempt 2(wrong again!):
My guess would be:
From @Rand al’Thor
I think it might be something to do with
the fact that all of the puzzlers mentioned in the question - Tom, SteveV, Jafe, Rand, elguest, hex, Bass - have tag badges (bronze, silver, or gold) in the riddle tag.
Which makes it ironic that
I just edited the riddle tag out of your question because it's not a riddle! :-P
Which then makes me think that the numbers might have something to do with
the requirements for earning a tag badge. Specifically, the number of answers/votes you need for a silver one is 4 times the number you need for a bronze one, while the number you need for a gold one is 10 times that, which comes to 1000 votes. I just don't see the relevance of 6 ...
But I seem to have the answer.
The number of votes you need for a gold badge is 1000, which is 10 times those for bronze.
I just browsed the six user profiles, and except for Rand al’Thor
and El-Guest, the remaining four have silver or below in the riddle tag.
This can be proven by using Roman numerals
Then for part 2:
10 = 1000 if we consider 0 to have no value - literally!