Sometimes I have text subtitles with these marks too. It's possible that it isn't caused by VLc (I've never seen something like that). Of course, I didn't see those subtitles. I have no idea how are these subtitles created, why someone put these marks in the "text". Maybe it's caused during some conversion or something.
But it could be also ssa or other special format. So... We need more informations or URL if possible.