I don't think there's anything wrong with upvoting your own posts either....I mean....there's a button specifically for that. I've only been here around 11 days or so and I just automatically started upvoting my own posts (I'm pretty sure the 'upvote posts automatically' button was defaulted to be selected and I just didn't switch it off).
I haven't heard any complaints about doing that either....granted.....my content is not pulling in huge rewards (at this point anyways), so maybe it does really have more to do with some people getting upset once rewards are larger, as you've stated. I haven't though, upvoted any of my own comments.....I always just let others do that for me (or not).
I think the whole intent is really to encourage good content though, of course, and the rewards and social norms on here seem to try to align with that. I think encouraging good content is important but I have heard others say that the rewards are not really based on good content. I like to believe they can be though as that seems to be the original intent here and the more the rewards actually reward good content, the better......in my opinion anyways.