Brill Academic Publishers was the launching customer of BPT. Many of the publications on its text editions platform Brill Scholarly Editions use BPT. For example, all publications that are updated regularly, such as the flagship products Jacoby Online and SEG Online use BPT to create and edit new content.
Of course, there are many other projects out there that use plain text that is then converted into some other format, like TEI. For example Papyri.info or OpenITI. See the beginning of this documentation.
Brill Academic Publishers has been using the BPT format since 2019. Two major lessons were learned in that time.
It is not so simple to mitigate this. An appeal to open science and GDPR may counter the users’ aversion to plain text, but it is ratio versus emotion. I guess we need better tools to help people work in plain text, tools that support rich text.
Regarding the second lesson: BPT differs from TEI in one respect: its commitment to stand-off annotation. Only very recently (2022) did TEI introduce stand-off annotation. Traditionally, TEI documents cram all information into a single document. This does not help with readability.
(Of course, there are other arguments why BPT might trump XML, such as the fact that XML is brittle,verbose, and unsuitable for publication on the web).