Is it rude to interrogate downvoters?

I'm very curious about the reasoning different people use when deciding to downvote a post or comment. Often, when something gets "heavily" downvot…

I down-vote bad writing and spelling, sometimes. Comma splice is a huge one, but “emails” and “literally” can get a knee-jerk down-vote as well.
“emails” as opposed to “e-mails”? That’s a new one to me, I’ve always assumed both are valid.
Both are equally valid, which is to say incorrect. Mass nouns get no S. You’d just as soon write “I got 3 mails from the mailbox” and wonder why you weren’t taken seriously.

Mass nouns get no S

More accurately, a mass noun cannot be assigned a grammatical number. For example, compare

  • *one bread, *two bread, *two breads, some bread
  • one sheep, two sheep, *two sheeps, some sheep
  • Asterisk means “agrammatical”. #1 shows “bread” is a mass noun, and #2 shows “sheep” isn’t, even if “sheep” doesn’t accept the ⟨s⟩. (It’s just a weird plural.)

    …that said I think your take is bad. “Countability” is rather unstable, specially if there’s some semantic pressure to keep both the countable and uncountable meanings. That applies to “mail”; in fact the word used to be only countable. (It meant “bag”. Nowadays that meaning is archaic, but still.) Add dialectal variation (e.g. Indian English speakers seem to be rather fond of using “mail” as a countable noun) and language interference, and the whole thing becomes an “I only accept when people use a language the same way as I do!”.