@kariboka@social.harpia.red Might be able to, but that might be a bit complex since XMPP has the same syntax as email (address@domain.tld), the way that Matrix is, it has a different syntax than email (@username:domain.tld) so the sign-up form could detect it differently than email. Which is why the requirement would be Matrix or Email required, not Matrix and Email required. Then you could have one single line in the sign-up form and it would still be familiar to most users.
The main suggestion isn’t simply verification of Matrix accounts but being able to use a Matrix account instead of email to sign-up to servers. Also to be able to use Matrix in addition to Email for account recovery. Would be an alternate method of verifying the account, as well as enforcing usage of Matrix usage if Lemmy admins desire that.
The verification of Matrix account ownership isn’t really the primary goal, it’s just a nice side effect. It wouldn’t be in effect though unless the server had one of the first two options checked, if it’s the other two options it wouldn’t need to be verified to be added.