It's awesome to see the match_selection feature get added! (I've found the WordHighlight package to be indespensible). Two requests fall out from this to make me move off WordHighlight though
-Don't require the selection to be non-empty (e.g. highlight "word-like" patterns that are under the point). Having to actually have a non-empty selection (that is on an exact word boundary no less) makes this a lot less "smooth/elegant" than WordHighlight.
-Allow the resulting highlights to be themed a bit. e.g. I have WordHighlight make the highlights have no outline, with a solid faint background. This makes the highlighting non-obtrusive for readability, but visible when you want to focus on them. The outlines make things look a bit more cluttered...
The combination of the above two features makes it so you just need to point at a variable and you see all the occurrences of it on screen right away, making manual search waaaaaaay less necessary, and skimming code a lot more fluid.
In any case - keep up the awesome work!