This is the same code as the famous "Highlight all occurrences of selected word", originally authored by Nicholas Sha, except I added the ability to customize the colors, ignore commented text, and match case. See "Selection Highlighter++" under the Edit menu.
For those who aren't familiar with this... this extension makes it to where when you highlight a word, VS will highlight all occurrences of that same word in the text view. (Yes, I know VS already does this to an extent, but VS only does this with actual code symbols.) This does it with all text just like the way Notepad++ does it.
I just starting learning extension development like, 2 weeks ago. So be gentle, this is my first time. (If it acts weird at start-up, toggle the "Include Comments" and "Match Case" menu items once or twice. It acted weird for me once, and that 'fixed' it. I'll try to fix it for real in a future release.)