alt Hacker News> The correct use is to check whether a submitted identifier contains characters that visually mimic Latin letters, and if so, reject it
That is a really bad and user-hostile thing to do. Many of those characters are perfectly valid characters in various non-latin scripts. If you want everyone to force Latin script for identifiers, then own up to it and say so. But rejecting just some them for being too similar to latin characters just makes the behaviour inconsistent and confusing for users.
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The correct approach is to accept [a-z][a-z0-9]* as identifiers and forbid everything else.
I agree that rejecting valid non-Latin characters in valid contexts is user-hostile, but I should be clearer about scope: this is specifically about machine-readable identifiers (slugs, handles, ENS names) where the character set is intentionally restricted, not display names or user-facing text.
The approach there should be what wongarsu describes below (imo), to style the UI so official accounts are visually distinct (badges, colour, etc.) rather than policing the character set.
namespace-guard is deliberately opinionated for the slug/handle case where you've already decided the output should be ASCII-safe. If your use case is broader than that, confusables detection without rejection is the right call.
What would make sense is to have a blacklist of usernames (like "admin" or "moderator"), then use the confusables map to see if a username or slug is visually confusable with a name from that blacklist.
I initially thought that must surely be what they are doing and they just worded it very, very poorly. But then of the 31 "disagreements" only one matters, the long s that's either f or s. All other disagreements map to visually similar symbols, like O and 0, which you should already treat as the same for this check
Not to mention that this is mostly an issue for URL slugs, so after NFKC normalization. In HTML this is more robustly solved by styling conventions. Even old bb-style forums will display admin and moderator user names in a different color or in bold to show their status. The modern flourish is to put a little icon next to these kinds of names, which also scales well to other identifiers.