I definitely agree. In my opinion, if you as a moderator are 100% sure that the comments are obsolete and not helpful anymore, just go ahead and delete them. Here's an example where I thought it might be helpful to leave my comment at least for some time, since it's not about a simple typo: Wann verwendet man „zu“ mit dem Infinitiv?
Personally, when I leave a comment indicating minor typos, I delete the comment myself as soon as the typos are fixed. Sometimes the author of the post leaves some "Thanks, done" type comment; then I also ask the author to remove that comment, and after the removal of the authors comment I remove my follow-up comment. (Yes, that's a bit messy.)