I can't address submissions, but I can however address posts:
The unfortunate problem with this is that often, there is no direct link between comment quality and the amount of karma you receive for posting it as several walls must first be breached before your comment is even seen.
Firstly, the quality of the article in question is the most important outside factor, if it is a fluff piece, apart from several posts about it being a fluff piece there will rarely be a fair amount of visitors to the comments section, whereas well written, high quality articles tend to drag a crowd, curious to know what their peers have to say of the subject in question.
Secondly, the position of your comment in the comments section can be a massive boundary, you will find that often, the comment at the top has the most replies, this has a direct correlation to it's position of course, people tend to read what the see first (and to reach the top, it must have been up-voted, leading you to believe it will add value to the thread) although, the more cynical side in me wants to believe that some people post on high placed comments simply to farm karma with their yes-man comments.
After being seen, there is the length of your comment, people bore easily and if your comment isn't interesting (to the person reading in particular) from the first instance then they will move on without properly absorbing your opinion.
After gaining the initial traction to be read, then and only then is the quality of your comment going to become a variable in the equation of how much karma you will receive.