Entering certain text into `spamcop.net/w3m?action=contactform&reason=Feedback#text` causes erroneous correction `<mark>`s to appear.

#### Screenshots

[^1]

[^1]: [`spamcop.net/w3m?action=contactform&reason=Feedback&details=Your+Invision+mail+servers+send+mail+with+unresolvable+hostnames.#text`](https://www.spamcop.net/w3m?action=contactform&reason=Feedback&details=Your+Invision+mail+servers+send+mail+with+unresolvable+hostnames.#text:~:text=Here%2C%20you%20may%20provide%20any%20other%20details%20you%20feel%20are%20pertinent:)

#### My Environment

I am utilising [`addons.mozilla.org/firefox/downloads/file/4957307/private_grammar_checker_harper-2.8.0.xpi`](https://addons.mozilla.org/firefox/downloads/file/4957307/private_grammar_checker_harper-2.8.0.xpi), on [`packages.mozilla.org/rpm/firefox/Packages/f5a0b5657837e72f15e323d0116c2f8f6d3a041facde934f788f708a9f2a8527-firefox-nightly-156.0a1-20260823213825.x86_64.rpm`](https://packages.mozilla.org/rpm/firefox/Packages/f5a0b5657837e72f15e323d0116c2f8f6d3a041facde934f788f708a9f2a8527-firefox-nightly-156.0a1-20260823213825.x86_64.rpm).

#### Additional Context

[`issues/4219`](https://github.com/Automattic/harper/issues/4219#issue-5240594903) exacerbates this.

Reproduce the issue at the linked spamcop.net contact form using Harper 2.8.0 in Firefox Nightly, then compare the behavior with issue 4219. Done means entering the affected text no longer produces erroneous elements in the form.

Written by the indexing model from the issue text.