Nickname blacklist regex help (potentially a bug?)

[Akiranya]

I'm using Essentails 2.19.7 and I don't want to allow the players to use some magic characters which are used as image placeholders in my server resourpack (in other words, I don't want players to use an arbitrary image from my server resourpack in their nicknames) So I write the following regex to only allow players to use Chinese, Hiragana, Katakana, and a-z A-Z 0-9 & #:

https://regex101.com/r/Qd9oxd/1

With the regex above specified in the Essentials config nick-blacklist, ideally the player can use any of the following nicknames:

1. 你好
2. abc
3. &#ffcc99你好
4. &7Hello
5. の

But in fact, the players can only use: 1,2,5 (which does not include any color codes)

What confused me the most is that none of the nicknames are matched in regex101, but Essentials thinks they matched the blacklist-regex... I would appreciate any help.

[Akiranya]

One thing just came into my mind: Essentials could potentially automatically replace the & character with § before passing the nickname into the regex predicate. And I found what I was thinking is correct! I add the § character into the regex and the problem solved...

It might be a good suggestion that Essentials delays the replacement of § character. So it firstly pass the original String into the regex predicate and then do the § character replacement, which would be more user-friendly I think. Or, add an comment on the nick-blacklist to indicate the automatic replacement so the users of Essentials know what they should use the nick-blacklist option in a correct way.