Devil's advocate:

If a country A decides to block twitter.com but forgets to ban x.com which remains available ... is Twitter engaging in illegality / violation of CDN terms of service?

Like most things in the legal system, it depends on intent. It's pretty obvious that twitter's rebrand to x.com was an actual rebrand and not some way of evading domain bans.

The author claims a reasonable intent and they give a traffic number that proves they're not doing "domain rotation".

>The author claims a reasonable intent

Right, I'm not arguing that they're guilty, just that the legal system doesn't operate off pure black and white rules like "if you have two seemingly unrelated domains then you're trying to evade bans".

>and they give a traffic number that proves they're not doing "domain rotation".

Are you talking about the part where they said "95% of our traffic through the main domain"? Without additional context behind that number it's a stretch to claim that "proves" they're not trying to evade bans. For instance if their country is banned in country A, but country A is a small country that only makes up 3% of their overall traffic, they can confidently claim "95% of our traffic through the main domain" while still theoretically using alternate domains for ban evasion purposes.

This has always been my concern about establishing a presence online. I've considered blogging about my experiences at work or the cool stuff that I've built and it feels impossible for me to know when I've crossed a legal boundary. How do I know for sure if I'm sharing proprietary stuff or confidential stuff. The lines of legality seem to get blurry real quick.

This is legally equivalent to "we have domain aliases". Lots of sites have those. Do you think that's really the problem here?

No, it’s technically equivalent. I be legally equivalent it would be required to prove (or disprove) intent.