Which font is it using? You can open up the developer tools, bring up the tooltip and then use the DOM viewer to navigate to the tag and look at the font.
You might have to play around a little, but make sure you only click/navigate in the DOM because it will hide the autocomplete dialog if you click in the client area.
If you find the font-family attribute, track down the one you actually have. CSS starts at the left and goes to the right until it catches it (in the example, I have Consolas but I don’t have Menlo). You should be able to then look at the font and see if it handles dashes poorly (from your screenshot, it looks like it is monospace except for the dash) or if you can install a new font that will do a better job.