Removing the colon appended to user mentions

I would like to remove the colon appended when autocompleting a user mention at the start of a message:
This colon is only appended if the cursor is at position 0 (this is also a bit inconsistent). I don't think it adds any special value and I think it's just an unnecessary extra for no reason.
A mention simply works by writing the name and then using the autocompletion to make the client make it into
`username`. The colon is not part of it at all.
The client only highlights the actual part of the mention (`x`) and ignores the colon. The colon does not add clarity as to what the mention is. It's only noise. I frankly don't see the value of it.
In a way, it also predefines a style of speaking. If someone wishes to put a colon after their mentions, they can do so by themself.

Removing the colon also doesn't really threaten compatibility:

The specification does not specify the colon either. It is entirely the client's decision: https://spec.matrix.org/v1.2/client-server-api/#user-and-room-mentions

Overall my argument is that the colon just does not seem very useful. If however there is a good reason for it, please let me know.

See also: https://github.com/vector-im/element-web/issues/22383

Start with the issue description and the linked Matrix user-and-room mentions specification, then follow the see-also Element Web issue #22383 to locate the relevant client implementation. Done means that autocomplete no longer appends a colon to a mention inserted at the start of a message, without changing the mention itself.

Written by the indexing model from the issue text.