I agree with this sentiment.
I believe that knowing your vote is worth a tiny fraction of another user's vote will dissuade some from even voting. (It would annoy me, certainly, if I knew I was 'worth' 1/20th of another user. Maybe there's some ego attached but unfortunately, that seems only natural.)
The 3 points mentioned can all be argued and there will always be exceptions to any rule. But as long as each factor (voting behaviour, submissions, posting) is calculated separately it all seems perfectly reasonable to me.
To me, I don't understand how anyone could argue AGAINST a submitter having a more valid opinion, if all other factors are equal.
I like the idea of each variable being 'added' to your voting power, which is then capped. That way, someone could theoretically rise to the cap through one of the 3 'paths' (but in actuality, probably no-one would do so - everyone at the cap having a voting strength comprised of all 3 factors).
I'm just some random guy. Don't let my words get you riled - I have my opinions but they're only mine.