This question asked in July explains why it is not possible for the time being to submit content in posts or comments that contains Unihan characters. It’s a spammer thing, fair enough.
As snailboat’s answer makes clear, the workaround for posts is to convert your Unihan text to HTML entities: these are parsed and appear correctly.
However, HTML entities are still HTML and as such are not parsed at all in comments, as this answer by AstroCB confirms. In other words, since Unihan glyphs are banned from both posts and comments and HTML entities are not parsed in comments, it seems to be completely impossible to post text containing Unihan glyphs in comments at all, except on sites where the ban has been manually removed, like Japanese.SE.
This seems like a rather substantial limitation. And in any case, the blanket ban on Unihan is unduly heavy-handed and inflexible (not to mention perplexing to the user, when the only feedback you get is “Body/comments cannot contain that content”).
In this comment, tchrist suggested that the ability to post Unihan glyphs could be made a rep-based privilege; that is, a certain amount of reputation is required to include these glyphs, otherwise it fails. A requirement of, say, 125 rep points would presumably cut off at least 99.99% of spammers, and it would have the added benefit of being able to maintain—and broaden—the restriction indefinitely to mitigate spam, while still allowing legitimate users to post relevant content.
(The feedback message would have to be improved as well, though; something like, “Due to large volumes of spam written in certain non-Latin scripts, you need at least 125 reputation points to be able to include non-Latin text in your post” or words to that effect.)
Can this be implemented?
Alternatively, as pointed out in Normal Human’s reply, since comments already require a certain amount of rep meant to deter absolute newcomers (and, by extension, also spammers), can the ban just be removed from comments and applied only to posts?
(Editing this just to bump it on the front page, to hopefully have some kind of discussion or feedback on the matter.)