I am getting started on the Blender Stack Exchange site and have asked a complicated question and am getting great answers. But I am told need 50 points to comment on answers. How do I deal with this?
You can actually always comment on a question you've asked or the answers on it, regardless of your reputation. Unfortunately, it looks like you have two accounts, if the question you're talking about is this one: Earthquake visualization in blender?
As such, you can't comment with this account because it doesn't recognize it as your question. To fix this, you'll need to request that your accounts be merged by going to the "contact" link in the footer. You really want to do this and make sure you're logged in and registered and have all of your rep in one place and so that you can respond to the people asking you questions.
It looks that you managed to create 2 different accounts accidentially
You always can comment on your own posts and its answers, but since you are logged in with your other account you cannot comment anymore.
I'd recommend you should ask to merge these 2 accounts. Here is a detailed description of the steps how to do so.