All Session messenger rooms are getting DDoS'ed with a flood of spam.

Our room is now in lockdown, no new posts.

Be advised simpleX could be a target next.  These anonymous messengers with zero credentials to make new burners can be easily flooded with bots.  Matrix and XMPP are tied to government domains, so it's easier to control where bots are coming from or verification on the big servers.

Here’s the key point:
The more control group owners have against DDoS of group chats, the less metadata protection the 1-on-1 chat users have. 

 Proof of work should've been baked into the protocol from the start.  

 maybe as an option on groups. but for mobile devices with 3 hops networking? takes the instant out of instant messages 

 You're not wrong, but I feel like it's a better option than wholesale deleting or blocking. I dunno.