I read this article already on how to force real names instead of usernames in post headers. However, I’d like to at least have the option if not the forced requirement that users’ real names be used for mentions in posts. Is that possible?

@メンションで実名強制

JammyDodger 2023 年 1 月 5 日午後 9:46 4

I’m not sure how a custom field would work here?

But there is this theme component which may do what you need:

「いいね！」 2

トピック		返信	表示
Discourse Show Fullname in Mentions Theme component	29	2308	2023 年 10 月 19 日
Full name @mentions Feature mentions	60	11830	2022 年 3 月 15 日
Change mention from username to a name? Support	5	927	2021 年 9 月 21 日
Can a Theme have a quote display real name instead of username? Feature	2	673	2020 年 5 月 22 日
Discourse Provide Full Name in Mentions Plugin	0	640	2023 年 10 月 2 日