Mentioning an account with dot in username doesn't work

[tastytea]

💡 Summary

I was trying to mention @digitalcourage.de@digitalcourage.video, but it generated a mention for @digitalcourage@my-instance.tld

🥰 Expected Behavior

Mentions do not stop at dots in usernames.

🤬 Actual Behavior

📌 Environment

Misskey version: 12.117.1
Your OS: Gentoo Linux
Your browser: Firefox 91.11.0esr

[acid-chicken]

Related to #8503 (comment)

[osak]

Came across this issue while looking into Bridgy Fed. It uses the domain name as the user name by default (e.g. @osak.jp@osak.jp), so it is difficult to interact with accounts on that service from Misskey.

[tamaina]

🔥

[tamaina]

mfm.jsの問題？

[samunohito]

mfm.jsの仕様ですね。
https://github.com/misskey-dev/mfm.js/blob/develop/docs/syntax.md#mention

1文字以上。
A～Z 0～9 _ -が含められる。
1文字目と最後の文字は-にできない。

とのこと。