Why do we only have post history? It seems natural that we should also be able to view a list of our own comments.
Actually, you can! Go to your profile, click "...", and then "History". Then click "Posts" to switch to "Comments". Unlike Reddit, other users can't see your comment history, only you can. Hope this helps :)
I think the drop down menu needs to be a little more obvious. Maybe put it under the header?
It could also help to make the options as individual buttons next to each other instead of a drop down.