Windows 8's default settings at Control Panel\All Control Panel Items\Display "Change the size of all items" is set to 125% by default (wtf?)
This make the highlighting in the hex editor offset by, I'm assuming 25%.
Ignore the OS specification on the side, that was for my initial bug report before I realized default font size were not the same.
Switching it back to 100% makes everything fine, so not a big deal, but I was getting used to 125% size (without my consent).
Edit: Tried to fix this, found you can find windows DPI setting using
// find windows DPI settings for selection offset
Graphics graphics = this.CreateGraphics();
winDPIpercent = (int)(graphics.DpiX * 100) / 96;
fontHeight = fontHeight * winDPIpercent;
fontWidth = fontWidth * winDPIpercent;
setting the fontHeight/Width as double instead of int, and modifying every instance of those variable being called to include a Math.Round( blabla, 0) at the latest possible point in the calculation.
Results were not concluant, the highlight offset was much better, but not good enough to be used as a fix