- Part of the protection Tor provides is due to having the single browser made specifically for Tor. Nearly everyone uses it; this gives you a sufficiently large crowd to blend into. There are fingerprintable clusters inside this crowd, but at least they are still large enough. By using any other browser, you make yourself stand out and even diminish the anonymity of the whole network a tiny bit. This can become a problem if enough people are using custom browsers. Brave in particular is also not restricted enough by default (no JS etc). Default settings for everyone matter.
- Brave's Tor feature wasn't thoroughly tested in real situations. AFAIK they had issues with it, and also warned users not to rely on it as it's not complete.
While I'm in agreeance with everything you've said it should be pointed out that Tor Browser doesn't ship with JS disabled either, it simply breaks so much of the web that they've concluded it's not reasonable for a browser to do by default if they want to attract new users.
Meanwhile, we know for certain that Firefox has played a role in multiple deanonymizations.
So I think the answer to question is - absolutely nothing. The very few missteps Brave has made get broadcast from the ends of the world. The fact the biggest thing people can find to complain about it is some crypto stuff, which is opt-in and easily completely disabled, or an autocomplete tagging a referrer - that was patched out in less than 24 hours, is strongly indicative of the quality and integrity of the browser.
That functionality (which would modify some literal URLs typed in by users, not just make autocomplete suggestions!) was present in the source repository for roughly a month and a half until it was disabled by default, and remained present as an option for over a year after that.
https://github.com/brave/brave-core/commits/master/component...
You may mean that it was modified less than 24 hours after users noticed it and raised an outcry, but that still doesn't exactly inspire confidence.
Can you imagine google chrome bringing Tor integration into their browser? Why not?
Further, there is no way to pre-emptively disable the cryptocoin elements on new profiles on the same Brave installation.
Chrome feels a lot faster than Firefox to me (Especially on Facebook!), yet I still use Firefox to resist Google's stranglehold on the web.
Hope you trust Mozilla with that same level of info (in twenty years)!
Misleading way to say more APIs, I presume?