However, when you disagree with someone, do you just tell them you differ and leave it at that?

• It's a non-Perl question - many web questions are non-Perl questions, even if a program written in Perl is involved.
• The question is too poorly phrased. It requires too much guessing what the problem is. This includes too much bad grammar, too many typos, and bad specification of the problem(s).
• The post is just wrong. (Probably the majority of my down votes fall in this category). This sometimes causes me to downvote every single post in a thread.
• People not reading what they are replying to careful enough, and coming up with code that doesn't meet the requirements given.
• People asking FAQs or trivial things that could have been found easily in the manual.

I also know the arguments why others don't downvote for the reasons I do. You don't have to repeat them - but posts that fall in one or more of the categories mentioned above decrease the value I get from perlmonks. Hence, they are getting my downvotes. And I'm not advocating anyone else should use the same voting guidelines.

Abigail