It seems that on VS2012 (July Update) the code coverage markers overlap the text in the editor. I originally noticed this when editing some F# projects, but it also appears to happen in C# (Its just a lot less noticable in C# because most C# code is heavily indented). See the FsUnit sample code below for an example:
[img=(- BROKEN LINK -)]Screenshot showing position of coverage markers[/img]
Edited 14 Aug 2012 18:30 UTC