[wallacoloo]

I was really surprised when the original article said mastodon was blacklist by default (and that instance whitelisting was only possible via forking the code!)

I’m actually not certain this is true. I used Mastodon briefly and I remember there was one account out there that auto-followed every user it saw tooting. That way that bot’s instance would build connections to every instance it could see, which gives both (A) metrics - you can get a rough estimate of how many instances are alive at any time - and (B) a way for instances to discover smaller/newer instances if they choose to (I.e follow this bot, and now the global feed visible to your instance sees just about everything).

If Mastodon is blacklist by default, then it must have some other discovery mechanism? Or maybe the terminology just isn’t being applied in the way I understand it (e.g. perhaps it is whitelist-by-default, in that you explicitly connect to instances of your choice, but this implicitly whitelists every instance that whitelisted instance is connected to, recursively, and the blacklist is built atop this)?

[skybrian]

I believe other instances get automatically subscribed (without admin's preapproval) when any user follows someone on the other instance.