See: https://devzone.nordicsemi.com/f/nordic-q-a/42606/nrf52840-doesn-t-advertise/166030#166030 - where I tried to @ mention Cyril but got cyril instead!
And no, it's not just a matter of typing the upper- or lower-case 'C' - the forum ignores that and suggests only the one name!
See also: https://devzone.nordicsemi.com/backstage/f/welcome-to-the-devzone/42127/how-to-mention-names-with-spaces
Another example here:
@Simon gives me several posssible names:
But none of them is the Simon that I was looking for!
1) there's something with users that have a space (" ") in their display names:
For example @firstname Lastame - typing @First with a space the user is not returned when @mentioning.
What we’ve found is that when typing @first name lastname in quick succession the user is returned despite there being a space. But if the user hesitates on the space for a moment the @mention functionality stops its search and fails to find the user. @mentioning would be improved with more of a timeout when inserting @firstname lastname.
2) In some cases, the user you want to @mention has not been designated a display name, or his displayname id the same as his username.Therefore you will not see the common displayname (username) in brackets, in the @mention search list. This could be overcome by us making it mandatory for users to create a displayname on sign up.
Anyways;I’ll ensure this gets raised as a product enhancement. Any comments on the above let me know.