I've gotten quite a few times "phantom" lines while editing an html file.
E.g.
Code:
112 <div> etc etc
112 <div> etc etc
There can be several occurrences of these phantom lines, and it doesn't matter whether the line contains code or comments.
It also does not matter whether it scroll the offending section off the screen and scroll back. The phantom extra lines are still there.
It seems to occur (tho I can't be sure) after I've hidden then re-expanded a section of code (using the -/+ on the left side). I can't say if this is a consistent happening either.
I have the latest 3.5 version. I don't remember this bug occurring in the previous version.