Previously I posted a question in this meta stack exchange about lack of up votes of questions, especially questions that have answers. Based on the answers in that post, it seems like multiple people on the meta site have the general philosophy that if the question was clear enough to answer, and showed a minimal amount of research effort, it is clear enough to up-vote. The philosophy has come up in other posts as well. So my question is, would it be inappropriate to let others on this exchange (who don't use the meta) know about this unspoken norm to encourage up-voting. Basically would it be inappropriate to post below an answer in a comment "Please consider up-voting all questions you answer. If the question is good enough to answer, it's likely good enough to up-vote. If you don't think an up-vote is appropriate you might want to consider asking a question in a comment, as opposed to providing an answer to an unclear, or obviously un-researched question." I suspect many users would find this comment offensive. Is this a really bad idea? I can definitely see downsides, like potentially it discourages answers. We already have a problem of posting answers in comments anyways.
Thanks for explaining the background and motivation; I think that helps with a picture of why you are asking as you do.
I know myself it can sometimes be frustrating at first, especially for motivated contributors, who may often be - very reasonably - wanting to participate in ways the software doesn't allow them to.
On your question, I'd think it reasonable only to a fairly limited extent: in particular, for users that answer many questions, and who show a pattern of not upvoting quite a few questions they answer (which, if you were able to look at my votes on my last ten answers, sure looks to be the case - I have not upvoted at least three of them), I think it may be okay to encourage them to consider it, once.
The difficulty, of course, is that you won't be able to see their votes, I think, only how many times they have voted, and how many net votes an answered question has received (with 1000 reputation you can see the split into up and down votes, though if you're clever you may be able to figure it out before then, with a bit of effort); so sometimes you'll be guessing.
So I'd be the ideal candidate for such a reminder, by the look of it, though in fact last year I was one of the top handful of voters on the site (I don't know exactly where that would be because I wasn't really paying close attention, maybe in the top 5, but it was between 3000 and 3200 upvotes over 2012, and I believe more than 60 percent of those up votes were on questions).
Interestingly, at one point last year, the site itself said something along the lines of "You have been upvoting a lot of answers just lately, but it's a while since you upvoted many questions, consider upvoting more questions"... which I have worked on since (and that's why my rate on questions is now over 60% of total upvotes).
So for some users at least, the site itself may remind them to upvote questions.
I think it would be good if the site encouraged the relatively new users to simply vote more (in what ways they're able, as they're able); many don't seem to remember to do it at all.
I think it is inappropriate to leave comments advising for voting (so +1 if I want to answer your title question).
On Meta we discuss and exchange ideas about many subjects in an attempt to promote and create guidelines that can help the site to develop.
People can have different interpretations, for example, about what a good question/answer is. Comments (repeatedly) pro-voting would probably annoy users and cause disagreements.
It is better when people come here spontaneously to take a second opinion and make comparisons with what they already think.
I rarely see comments which asks/advises voting. What I sporadically see are comments asking for the OP to accept an answer when he/she clearly speaks through comments that a specific answer solved his/her problem.
See this thread for more info: Is it wrong to ask a user to accept an answer?