As I can see, this was sadly not considered for the 2.0.0 release. Would it be possible to address this in a future 2.0.x or 2.x update?

font rendering for icons can still look very awkward in some browsers and operating systems

Can you provide a screen shot where one of the MantisBT icons looks very awkward?

That part of the comment was more a generic disadvantage of font icons - the Mantis icons look mostly okay here (with a few odd pixels here and there on Firefox).
I made this proposition more because font icons have already been called out as being a bad technology in the past (see my list of disadvantages in the description, in particular the point about dyslexic people).

The first mis-rendered become obvious now. The attached screenshot is taken with Firefox on Windows 7 at normal DPI settings.
As you can see, the "normal priority" icon is not symmetrical, but when zooming in you notice that it should be.
Same with the status icon, which looks very ugly with rounded edges at the bottom but not at the top. I wonder why you insist on using an icon font for something as simple as a square with rounded corners - this can be resolved using an inline-block with border-radius in a much more elegant way, and it will even work when the user overrides their fonts.

font-icon.png (1,376 bytes)   

font-icon.png (1,376 bytes)   

Same with the status icon, which looks very ugly with rounded edges at the bottom but not at the top.

I was not able to reproduce it using FF 51.0.1 on Windows 7, Windows 10 and macOS 10.12.3.
It looks not 100% perfect, but I get rounded edges on the top.

I wonder why you insist ...

I don't see anyone insisting on anything.
There is just no one at the moment who takes the time to enhance it.

It looks not 100% perfect, but I get rounded edges on the top.

I think it depends on many things, including the moon phase. :) No, more seriously speaking, it probably depends on the exact x/y position where the box is rendered on-screen, and maybe even graphics drivers. I took the screenshot above with Intel integrated graphics, but on AMD graphics I get a slightly rounded edge at the top (but still less rounded than the bottom). This does not happen with SVG icons. So it really would be preferrable to switch from font to SVG icons in a future release.

it really would be preferrable to switch from font to SVG icons in a future release.

While I fully agree with your advice on principle, to be frank I don't see this happening any time soon; MantisBT 2 relies heavily on a bootstrap template named Ace, and I'm afraid that with our limited resources we won't have the bandwidth to implement such a change in the near future.

@syncguru maybe you care to comment.

We could at least think about distinguishing between using fonts for icons and using fonts for rounded squares.

I'm not familiar with Bootstrap so I don't know how complicated it would be to e.g. exchange the icons in the main menu, but e.g. replacing the colored squares, priority and attachment icons in the bug tables should be relatively trivial, because all that needs to be done is replacing a styled HTML element with an image element. Of course it's a bit of work, but Bootstrap shouldn't get into the way there. It's only a partial solution but probably still better than nothing, and it will look better on various clients, too.