HNtitles is a browser extension for Firefox and Chrome that "unmoderates" titles of Hacker News stories: it displays the content of the title in a caption as it was before being moderated (changed).
Two reasons:
A cron job downloads titles from the newest page at regular intervals and stores the original titles.
The extension scans titles on HN pages and compares them to the stored version using Levenshtein distance; if they're different it shows them with an asterisk; if they're very different it shows two.
Titles marked with an asterisk display the original title on a mouseover (or long pres on mobile).
Available for Firefox and Chrome.
Here's a great post by dang about moderating HN titles.