I don't even touch browsemarks. I open some settings dialog and close it even without modifying the settings and then bang - I have a couple of these. Unfortunately it's so inconsistent I can't reproduce it.
By default browsemarks are set, if you press left mouse-key for more than 200 ms in a line.
The browsemarks are the three dots in the left margin.
If you have opened "Settings -> Editor" and left it with "OK" the bug appears, because the editor does not take care of the margin settings of plugins.
All lines that contain browsemarks wil become blue.
I will commit a fix for this issue, if I have tested it enough.