You're comparing different versions of the standard.

If you look at the current version:

• https://github.com/toml-lang/toml/blob/main/toml.md

and the current ABNF:

• https://github.com/toml-lang/toml/blob/main/toml.abnf

you will see that %7f is now allowed in comments.

This was a change that we made explicit in #924. It could be reverted if we merged #996, which I'm personally opposed to doing. So keep an eye out for this. By the time v1.1.0rc1 is released, this matter will be resolved, one way or another.

Am I? I'm comparing the specification 1.0.0:

Control characters other than tab (U+0000 to U+0008, U+000A to U+001F, U+007F) are not permitted in comments.

To the grammar tagged 1.0.0

toml/toml.abnf

Line 39 in 8eae5e1

non-eol = %x09 / %x20-7F / non-ascii

If it's going to be fixed in a later version then it's not a big deal, but it does seem to be a real mistake in one of the two documents.

Indeed! I'm pretty sure the intent was to forbid "Control characters other than tab", like the written spec says, so the ABNF is wrong in allowing U+007F.

But in any case it's a bug in one of the spec documents and the next version must fix it. So it's good that the current mainline already fixed it by allowing nearly all control chars.

1.0 was fixed in #812. We can discuss reverting #924 in the above PR.

Closing this out since that has been changed on main and will be resolved once 1.1.0 is out "soon". :)