TestNoSecondFenceRule's delimiter-only detector misses a private toggle written as a literal regexp that matches a run (for example a pattern of 0-3 spaces then a backtick or tilde run, with a length check) or as byte comparisons on the first character; its doc says a pattern 'assembled at run time' escapes, which understates a literal regexp. Extend the detector to regexp literals whose pattern can match a fence run, and to first-byte comparisons against a backtick or tilde, or narrow the doc to the truth.

TestNoSecondFenceRule's delimiter-only detector misses a private toggle written as a literal regexp that matches a run (for example a pattern of 0-3 spaces then a backtick or tilde run, with a length check) or as byte comparisons on the first character; its doc says a pattern 'assembled at run time' escapes, which understates a literal regexp. Extend the detector to regexp literals whose pattern can match a fence run, and to first-byte comparisons against a backtick or tilde, or narrow the doc to the truth.

Grounds

• pursued: a private toggle in either shape now fails a detector; a planted regexp run toggle or ln[0] == '~' toggle passing both detectors would show it wrong