User blog comment:MarkvA/Gamescom - Assassin's Creed III Preview/@comment-5019018-20120816202032/@comment-4564231-20120817181836

Well, first of all, I don't use the visual editor so I can't tell you about that. But I'm sure it works in source mode. Just make sure you have the spell-checker enabled:
 * 1) Go to Wrench menu\Settings\Show advanced settings\Languages and click "Language and spell-checker settings".
 * 2) Select a language that can be used for spell-checking. English cannot be used but English (United States), English (United Kingdom), etc can be used - it should say so.
 * 3) Check "Enable spell-checking" and save your settings. Now the spell-checker should be active for everything =)