Bugzilla

AS a separate issue to the bug Magnus mentioned....
Folders that have Italicised and greyed out font are set up as 'no-select' folders meaning they do not contain emails but can contain folders that do contain emails.

I have created an 'italised greyed out' folder deliberately in a gmail account.
In my gmail imap account the folder called 'Testing' has italised and greyed out font and it contains a normal folder called 'Sub Test'.

When accessing server the folders/labels do not look like a 'no-select' folder. They are required and cannot be removed via Thunderbird if they are a folder containing other folders etc.

I've included the image on how I set up 'Testing' as a no-select folder.
First I added 'Testing' as a new top level label/folder as a sub to [Gmail] /
Then I added another label which INCLUDES the top level name: 'Testing/Sub Test' and set as a sub to 'Testing/'
Thus 'Testing' is now a no-select folder containing 'Sub Test' which is a normal folder.
Basically, adding the tier directory to the sub folder made that top level folder a no-select folder.

If I had added the sub label and DID NOT includes the top level name: 'Sub Test' and set as a sub to 'Testing/' then both folders would be normal folders. 

I suggest you access your webmail account via abrowser and look at the labels/folders you created. If it works the same way as the gmail example then Edit the sub folder name so it only contains name of folder.  This may help you to resolve the 'italised' issue and remove the 'no-select' flag.

AS a separate issue to the bug Magnus mentioned....
Folders that have Italicised and greyed out font are set up as 'no-select' folders meaning they do not contain emails but can contain folders that do contain emails.

I have created an 'italised greyed out' folder deliberately in a gmail account.
In my gmail imap account the folder called 'Testing' has italised and greyed out font and it contains a normal folder called 'Sub Test'.

When accessing server the folders/labels do not look like a 'no-select' folder. They are required and cannot be removed via Thunderbird if they are a folder containing other folders etc.

I've included the image on how I set up 'Testing' as a no-select folder.
First I added 'Testing' as a new top level label/folder as a sub to [Gmail] /
Then I added another label which INCLUDES the top level name: 'Testing/Sub Test' and set as a sub to 'Testing/'
Thus 'Testing' is now a no-select folder containing 'Sub Test' which is a normal folder.
Basically, adding the tier directory to the sub folder made that top level folder a no-select folder.

If I had added the sub label and DID NOT includes the top level name: 'Sub Test' and set as a sub to 'Testing/' then both folders would be normal folders. 

I suggest you access your webmail account via abrowser and look at the labels/folders you created. If it works the same way as the gmail example then Edit the sub folder name so it only contains name of folder.  This may help you to resolve the 'italised' issue and remove the 'no-select' flag. Remember to edit the lowest folder in the tier first working your way upwards.