The reason for references is because very few of us as clients have well-known presences within the scene or on the internet. There are not review boards for clients other than blacklists for those that are dangerous. Deposits are a different question as those are in place to help mitigate if/when a client doesn't show up for some reason (legitimate or not) since Dommes must prepare for a session in various ways (hair/makeup, getting dressed up, possibly travel and facility fees) that they totally lose out on if the session doesn't happen. There is no client equivalent for this.

A blue checkmark means Twitter knows their legal identity. Eros has the same thing. It has nothing to do with whether someone is trustworthy or has any clue what they are doing from either a safety or fun perspective. So, while I support your personal decision of setting that as a requirement for you to book, I don't see much value in it as I trust my own research a hell of a lot more than Twitter's.

YMMV...