Made a void age, started building a space station with turtles, some time after ~30-45k canvas blocks were placed I attempted to teleport to the chunk-loaded dimension using a mystcraft book and was disconnected. Subsequent attempts to reconnect failed with a socket error unless teleported elsewhere by another user. Restored a backup and tried again only to encounter the same issue around the same point in the build. Apparently canvas blocks weren't meant for such a massive scale, the server continues to run but users are disconnected in the age.

You are correct. Canvas blocks weren't mean for such massive scale.

Possibly connected to Thaumcraft's too-much-warded-blocks error. Apparently TE packets are ineffective when dealing with tens of thousands of tile entities.