I rather deal with moderation by myself by choosing who to follow, than rely on Twitter moderators and their moral compass to decide what's OK and what's not.

The fact that there is almost no point of contact for average Japanese person in life to anything not Japanese, still in this day and age, seems too often overlooked. Here, everything from baby formula to grad school textbooks on nuclear physics are available from local producers or at least in thoroughly rewritten versions. Average scores for TOEIC Reading/Listening test[1] for University students in English language major is ~600/990. 450/990 for CS students btw(!!) and both without doubt heavy uses of sophisticated test-taking techniques.

And it's the same even for Twitter: Everyone you follow speaks solely in your language, and has zero contacts with anyone who don't. Anyone who aren't speaking your language always seem total Martian and the languages don't even translate. Maybe you would come across couple quote-tweets per day from influencer types explaining peculiar foreign contents. You'd know that the domain name of the service is registered to an address in San Francisco, CA, USA, which is supposedly an area on a land, and that'll be the whole global experience you would passively receive on Twitter as a Japanese user.

1: which is apparently almost like a sanity check for a 5th grader, like the hardest challenge is finding the correct store hours on a flyer printed on the test book by multiple choices, literally, but the questions are also written in the same language as the flyer, so...

Ah yes, the token Nazi argument. Twitter is now the official Nazi hangout?

You're being manipulated. None of your sources provide any evidence of there being more "hate" speech on Twitter now than before. None of your sources provide any evidence there's more "hate" speech on Twitter than Facebook, Mastodon, Reddit, your favorite video game, etc. None of your sources even provide specific examples of what this "hate" speech actually was.

It's a big "trust us" thing. You're being manipulated.

hmm, they have an odd way of saying that then.