I do not think blogging about this openly is the right way to go
While I agree that sensitive topics should be handled carefully, I think that it is hard to find a better way to expose such an issue on Steemit. Maybe contacting Steemit Inc. directly instead of blogging it...?
Two aspects are important here:
-1- implementing your memo rejection suggestion (via [email protected])
-2- protecting the accounts / wallets involved, via notifying them (via email if possible) and urgently suggesting to change their keys ASAP.