I know I can increase the zoom or write a chrome extension to change it, but I think increasing HN's color contrast overall could help lots of readers.
That's one of many passive aggressive bits of operant conditioning pg originally added for quality control - meant to punish text-based posts by making them more difficult to read the longer they are. This is to discourage people from using text-based posts as an ad-hoc blogging platform, and make them as short as possible.
So no, that probably isn't ever going to happen.
Remove or modify the redundant line about flag/hide/fav... etc. Put it on a right click, put it as a mouse-over or as a button. Don't use half the screen.
It is better design to eliminate redundant non-content.