ISpellCheckProvider Puzzling Behavior

[TinoDidriksen]

I have implemented an ISpellCheckProvider and it works, but also doesn't (locale kl-GL installer; source).

If I use the official https://code.msdn.microsoft.com/windowsdesktop/spell-checking-client-aea0148c sample code, then everything works as expected and words get suggestions.

From any other MS-provided client, such as Windows itself or Skype, the word gets marked as wrong but the suggested action is to remove the word entirely, as if the response code is CORRECTIVE_ACTION_DELETE. But the debug log is clearly showing a return value of CORRECTIVE_ACTION_GET_SUGGESTIONS. So that makes no sense, as it all goes via the same MS-provided spell checker host handler. I can only conclude that MS implemented their own clients incorrectly...

Seems nobody else in the world is making spell checking providers using this API, and it's nigh impossible to get hold of someone at MS who'd know.

(originally asked on MS TechNet and Stack Overflow)