VisualSpellCheck will allow you use your spell checker in the Visual mode of the editor. FANDOM have the editor configured to disallow spell checking for some reason, this will override that and turn it back on.
Note that the editor displays its own right click menu which gets in the way. To access the corrections menu when right clicking on a red squiggle you must hold down Ctrl and right-click. This will bypass the editor's menu and give you your browser's normal right-click menu instead.