I don't think it's a matter of bandwidth. The document is being served up just fine; the only feature that seems to have been disabled is real-time commenting.

I don't think it's a matter of bandwidth. The document is being served up just fine; the only feature that seems to have been disabled is real-time commenting. Google Docs, like most of their applications, is built on a highly available, globally-distributed database. (There's evidence that it was using Megastore as of a couple years ago, and I wouldn't be surprised if it's now been migrated to Spanner.) That lets them scale to effectively infinite numbers of users, but it doesn't solve the problem of handling thousands of concurrent readers and writers all contending for the same individual rows in a multi-TB table, from multiple datacenters around the world.