If you didn't know already, there is a "showdead" option in your profile, so you too can view comments by banned people.
Checking your profile I see comments that you've made and that do show up, as well as people replying to you, and you replying to them.
So what do you mean by "comments don't show up"?
sometimes i bother to click unflag, others the article is nowhere to be found in a quick glance, so i just go on
The karma on comments is hidden, so there's no way for you to see that your comment upvotes aren't having an effect.
I don't know if there is any logic to subtly munge the visible karma on articles here; I know that Reddit does this, so upvotes there are not always immediately visible.
You had me right up until:
And did you have any comment in the 15 days before this?
If you can point to a specific comment that's not showing up, I can look into it. Karma scoring is more complex than just counting upvotes, so don't expect predictable results.