I looked into this for a while, and while I don’t really know what I’m doing, here’s some kind of interesting findings and speculation:
WaniKani / Radical / Guard for me on Chrome:
WaniKani / Radical / Guard for me on Firefox:
Here’s an experiment with HTML on the forum:
for me on Firefox:
for me on Chrome:
豚 has a non-font variant across languages (this is the unihan thing described here), but it seems like 兑 on chrome stands out and gets a different font specifically when trying to be displayed as Japanese.
Also!
If I use developer tools to tweak the language to “zh” instead of"jp" in the radicals page in Chrome, I get the Firefox version.
But if I do the same in Firefox, nothing changes.
So, my conclusion is that because as @Mike_Nekoski pointed out, 兑 isn’t used standalone in Japanese, BUT Wanikani specifies “ja” as the language for their radicals (since they teach Japanese after all), in at least Chrome, that causes it to stand out.
Other font differences are NOT noticeable because the language mismatch is not present.
My guess (completely speculating) is that that’s because in Chrome, because of a quirk or a bug, the fallback for “oops this is definitely a Chinese character but I’m supposed to be outputting Japanese” is “okay output it in the default Chinese font,” which in Chrome is more… serify, and thus noticeable.
Whereas in Firefox, either the default is “okay output it in the specified font anyway” OR… the Firefox default Chinese font is just like, the same as the ones used on these pages or something.
I’d be super curious if someone knows better or if that lines up with a more knowledgeable person’s take!
I’d also be very curious to see any existing developer discussion about this very specific edge case.
if (IF) I’m right, Wanikani could fix this extremely minor display issue by specifying the language for radicals affected as Chinese, or replacing them with static images as someone said other radicals already are. But it seems not really worth it to me, and honestly like it could (arguably) maybe be on Chrome to fix.
(and again I’m not at all a web developer and could easily be wrong or have weird options somewhere I forgot about)
(I was also logged in on the Chrome examples and not logged in on the Firefox examples, but I sure hope that has nothing to do with it)
P.S.: @Brave-foot That “saw” radical issue is something different I think, since that one appears to use a png, rather than an actual character. What page is the first image from? I don’t recognize it.