Egregoros

why does this say 'by default', not only it's not configurable on Mastodon, but the values are not specified in /api/{v1,v2}/instance

it makes sense for some other values, like max post length, which even though not configurable, is defined by Instance object and app devs can adhere to it. But Mastodon doesn't specify this. GoToSocial has an extension for this (configuration[accounts][max_profile_fields]). Pleroma has an extension under its own namespace (pleroma[metadata][fields_limits][max_fields]) and it's used by non-Pleroma backends as well. Mastodon doesn't.

guess we'll have max_profile_fields soon https://github.com/mastodon/mastodon/pull/37535