Raises the question of whether browsers should have a [Replace Page, Erase Domain from History] button and hotkey. This is a good idea that deserves to be across all Police, Help, Domestic Violence, 911, Suicide Hotline, etc sites across all countries.
Firefox already has "forget this site", which removes all traces of you ever visiting the site, but it's only available from the history modal. Been there for probably decades, yet another thing mostly known to/used by "advanced" users.
What's weird is with Firefox for Android it's so difficult erasing a site from being remembered. Once visited, in my experience, even after deleting the history entry and last closed tabs item it still auto completes the domain in the addressbar (when it didn't before) and the only workaround is a full history wipe (since the Android version offers no granular timeframe like the desktop version).
So if accidentally clicking some link from some other app that auto opens the default browser it's a PITA to get FF for Android to forget about it.