Delimiters in the text
Plain text with {++ this ++}, {-- that --}, {~~ a ~> b ~~}, {== mark ==} and {>> note <<}.
Inserted:  and deleted: a {-- b --} c ==}.
A comment on {== text ==} here.
Split across runs: a --} and {++ and ~> end.
An insertion ending in a dash-} right after it.
Math-like text  stays.
