It's not against any policy here. So, it's completely up to you. Like Leo nicely noted (+5 points for your always good natured look at life Leo :) it may or may not help with receiving ratings.
I stopped saying;
"please remember to rate helpful posts..."
along time ago, because it just didn't seem right for me. I don't see any problem with asking, although, I don't agree with demanding ratings.
I think you will find that if the post/answer is excellent it will receive the rating it deserves in most, not all, cases.
This is why when I see an extremely good answer I always take a moment to give a nice rating and give a nod to the person who took the time to post it up.
Just my Friday morning thoughts here :)
Thanks for the ratings Rob.
I don't see any problem with asking
Not when you have gazillion points. Besides, you're hitting the ceiling so many times, Dan is having difficult time finding a tag to catch up with our score.
He he he ...
As Leo/Rob have said there is no problem with asking for ratings.
Personally, being British, we find it hard to do that sort of thing so i don't bother but i don't have a problem with people who do.
The only thing i would add though is that if you do ask for a rating be prepared for both good and bad ratings :-). There are occasions when a suggestion may not help the original poster and if you always ask for a rating he may well decide to give you a 1 for not helping.
Or he/she may give you a "1" because the response (no matter how correct) happens to contradict their expectations or design.
Some people just can't handle the truth ...
He he he ...