Link is detected without the emoji in my app. You might wanna hardcode the link as https://en.wikipedia.org/wiki/😂
[https://en.wikipedia.org/wiki/😂](https://en.wikipedia.org/wiki/😂)

Link detection is flaky as hell, especially for special characters. They rarely work reliably. URLs themselves don't contain unicode. They use basic ASCII and anything beyond that needs to be encoded in some form. The link you posted isn't a spec-compliant link, it only works because Lemmy apps and browsers are nice and do the conversion to the real URL for you. According to the spec:

When a new URI scheme defines a component that represents textual data consisting of characters from the Universal Character Set [UCS], the data should first be encoded as octets according to the UTF-8 character encoding [STD63]; then only those octets that do not correspond to characters in the unreserved set should be percent- encoded. For example, the character A would be represented as "A", the character LATIN CAPITAL LETTER A WITH GRAVE would be represented as "%C3%80", and the character KATAKANA LETTER A would be represented as "%E3%82%A2".

If you use usernames as identifiers (which, again, are optional) like Lemmy does, databases and external entities will use the percentage URLs, not the readable ones. Unicode domains will have their xn-- form stored as well. It's up to apps and browsers to decide those and turn them back into unicode. It's not really relevant what apps and browsers show you when it comes to the technical interoperability of users.

ActivityPub itself has wide support for various languages, including having different names and content for different languages. The username (actually preferredUsername) is transmitted through JSON, which is by definition UTF-8, so most encodings in use today (not that weird Japanese one and that other Asian encoding that's not UTF compatible) will Just Work™ assuming the necessary URL encoding and decoding logic is added in the right places.

I think Lemmy can be patched to accept unicode characters as usernames, as the current limitations in code and in the UI are just choices made during development. I don't think it'll add much, though.

Using ASCII in URLs is simple and is less error prone than "supporting" unicode via percent encoding. It is also just a convention to use ASCII for usernames in many platforms. ASCII is also supported out of the box in major OSes while some unicode characters might not. What about impersonation? And what about people trying to type in the username of someone that uses unicode? It is not logical to use unicode in this case.

This user’s name is displayed in Arabic, although the characters in the URL are Latin.

Communities display names: https://lemmy.ca/c/maroc

I guess it could work for users display names too

There is also the risk of homograph attacks. The link below is for domain name encoding via IDN, but the same applies to usernames. You could easily impersonate another user by having chars that look similar.

https://en.wikipedia.org/wiki/IDN_homograph_attack

Because URLs are usually in ASCII. That was a standard. Check RFC 1738 and 3986. Now, you can use percent encoding, but why use that. It just complicates things.