Unbreak your paragraphs
Line breaks end up where you don't want them constantly: PDFs break every visual line, plain-text emails hard-wrap at 72 characters, subtitles arrive one fragment per line, and terminal output wraps at the window edge. Deleting the breaks by hand is exactly the kind of tedium a browser can do in one pass.
The three modes cover the three real cases: flatten everything to a single line, unwrap lines while preserving paragraph boundaries, or remove only the empty lines. Whitespace cleanup — double spaces, trailing spaces — is handled in the same pass.
Related fixes
If the text also carries Markdown symbols, strip those with the Markdown remover. If lines refuse to join even after unwrapping, the culprit may be an invisible Unicode separator — run the invisible character remover to find it.