Fix folding of long comments of unfoldable characters in email headers

[sethmlarson]

Linked PRs

• gh-143935: Email preserve parens when folding comments #143936
• [3.14] gh-143935: Email preserve parens when folding comments (GH-143936) #144034
• [3.13] gh-143935: Email preserve parens when folding comments (GH-143936) #144035
• [3.12] gh-143935: Email preserve parens when folding comments (GH-143936) #144036
• [3.11] gh-143935: Email preserve parens when folding comments (GH-143936) #144037
• [3.10] gh-143935: Email preserve parens when folding comments (GH-143936) #144350