Is this a hack? Yes. Hacks are replaced by standardized and better approaches (especially when better approaches are available now. "Fixing" this means removing it in code in place of a more logical approach. Where a triangle is really a triangle, not a rectangle with no dimension.
Part of web work is knowing immediately what you're dealing with. dimensionless rectangles that show up as triangles is a layer of complexity (hack) that disrupts flow.
I suppose I'll understand once I realize what you mean by "fixing" is actually "replacing". Specifically with your preferred method of accomplishing the same thing.
You aren't one of those programmers that can't help themselves in "fixing" everybody else's code that comes across your desk because they didn't do it the way you would, regardless of whether it works or not? I mean, the attitude I'm sensing in your text suggests that, but I'm sure you're a better person than that in real life.
"fixing everybody else's code that comes across your desk because they didn't do it the way you would"
that's the real world of design and collaborative environments. Branding, code quality, standards they all start with setting a direction that makes sense in order to improve efficiency across multiple disciplines and experience levels.
Hackey fixes have always been available. Instead of using h3 tags you can use b tags and scale them up to a particular font size.
Even when something works, you have collaboration and reputation to operate by. Case in point: Somebody actually had to create an animation to explain what the hell is going on with this hack to people who already know html and css, whereas with a unicode character or SVG you wouldn't have to have meta instructions. You could say good code or technique often requires no explanation.
Part of web work is knowing immediately what you're dealing with. dimensionless rectangles that show up as triangles is a layer of complexity (hack) that disrupts flow.
Get it?