I am ready to accept the reasoning behind treating Gmail as a special case, and disallowing the use of user-specified folder as the trash folder.
But I think that lying to the user is unacceptable. If user's selection of the trash folder is going to be ignored, the user must be told so. Either by not allowing him/her to select that option, or at least by showing them an error message like "this option does not work for Gmail". Currently (52.1.1, eight years since the bug was reported) Thunderbird lets the user select the trash folder, but silently continues to use a different folder.
I am ready to accept the reasoning behind treating Gmail as a special case, and disallowing the use of user-specified folder as the trash folder.
But I think that lying to the user is unacceptable. If user's selection of the trash folder is going to be ignored, the user must be told so. Either by not allowing him/her to select that option, or at least by showing them an error message like "this option does not work for Gmail". Currently (52.1.1, eight years since the bug was reported) Thunderbird lets the user select the trash folder, but silently continues to use a different folder.