code appearing in comments

When I edit comments, or posts for that matter, when I click “Edit Comment” as the Save of the final copy, I frequently lose line feeds. On the next Edit, there is code inserted, such as </br> or <p>, or font code, even though code view is not enabled (and doesn’t exist for the edit comment mode). On the save of this, the code appears in the posted text and has to be edited out to get a decent copy. Sometimes it takes several edits to get a decent copy with the line spaces still there, but the code not appearing as visible text. Am I doing something wrong, or is there a bug in this area?

I’m using a third party theme, but it appears to me that the editing function exists just in the core WordPress, not in the theme area, so I don’t think the theme is causing the trouble.