I work on infrastructure at Discord. Our voice and video infrastructure gets attacked quite frequently and we have pretty good tracking about which ASNs the traffic is coming from as part of our mitigation processes.
Anyway, Choopa is a common source of DDoS in our reports, so I can corroborate the OP's comment to some degree. They aren't the largest we see, but they're in the top 10 sources for us.
As someone who used to work for a company that hosted large-scale gaming infrastructure, I can confirm that Choopa was a common source of DDoS. DigitalOcean, too, and lots of eyeball providers. Any provider who allows credit card payments has issues with outbound attacks, and some are better at responding quickly than others.
It got so bad we ended up building and deploying our own line-rate packet processing engine at our network edge to be able to deal with the weird UDP protocols gaming uses.
It's OK to use guards for yourself because
1) there are thousands of non-public guards(bridges) 2) you choose the path to the rendezvous point 3) middle nodes don't know the type of the traffic
Also there are a few things wrong with your article.
This is not true. The spec does not specify that. Choopa LLC is not regularly used by hostile actors. You can't say that citing one report. Not true with rendezvous points.