Bugzilla

People are still asking for this in the Support Form.
If someone deletes an unread email in error, it is auto marked as read and moved to  Deleted.

There is no reason to do this other than helping those who get annoyed when the 'Deleted' folder showed as bold font. Basically doing it's job. 
Now, some people may prefer that option.
Maybe the same people like all Spam mail to get marked as read as well for the same reason.

I do not want anything to be marked as read by Thunderbird in the background if it has not been manually marked as read or opened and auto marked as read.
It is not for a developer to dicate what emails in my mail accounts should be auto marked as read.

It is not correct to mark unread deleted mail  as 'read' by default without providing an override. 

Removing preferences because a developer does not use it is not sensible.  You cannot approach program creation on that basis. I'm sure no developer would actually mean that, perhaps it was a slip of the tongue or misunderstood.

Even spam has a setting to mark as Not Junk as unread. 

Please provide the following to find a permanent solution and fix this age old bug.
1. create the preference to choose whether  unread mail should be auto marked as deleted upon deletion.
2. Fix the 'Undo deleted message' to restore the 'unread' status, if that was the status prior to deletion.

People are still asking for this in the Support Form.
If someone deletes an unread email in error, it is auto marked as read and moved to  Deleted.

There is no reason to do this other than helping those who get annoyed when the 'Deleted' folder showed as bold font. Basically doing it's job. 
Now, some people may prefer that option.
Maybe the same people like all Spam mail to get marked as read as well for the same reason.

I do not want anything to be marked as read by Thunderbird in the background if it has not been manually marked as read or opened and auto marked as read.
It is not for a developer to dictate what emails in my mail accounts should be auto marked as read.

It is not correct to mark unread deleted mail  as 'read' by default without providing an override. 

Removing preferences because a developer does not use it is not sensible.  You cannot approach program creation on that basis. I'm sure no developer would actually mean that, perhaps it was a slip of the tongue or misunderstood.

Even spam has a setting to mark as Not Junk as unread. 

Please provide the following to find a permanent solution and fix this age old bug.
1. create the preference to choose whether  unread mail should be auto marked as deleted upon deletion.
2. Fix the 'Undo deleted message' to restore the 'unread' status, if that was the status prior to deletion.

People are still asking for this in the Support Form.
If someone deletes an unread email in error, it is auto marked as read and moved to  Deleted.

There is no reason to do this other than helping those who get annoyed when the 'Deleted' folder showed as bold font. Basically doing it's job. 
Now, some people may prefer that option.
Maybe the same people like all Spam mail to get marked as read as well for the same reason.

I do not want anything to be marked as read by Thunderbird in the background if it has not been manually marked as read or opened and auto marked as read OR has been put in Deleted folder by a filter I created.  It is only for me to choose whether a deleted item should be auto marked as read.  It is not for a eg: developer to dictate what emails in my mail accounts should be auto marked as read.

It is not correct to mark unread deleted mail  as 'read' by default without providing an override. 
Even spam has a setting to mark as Not Junk as unread. 

>Would you be satisfied if we added the hidden pref, got numbers on how many people used it, and then removed it if fewer than, say, 2% of our userbase switched it on? 

Yes, add the pref - No do not remove on any basis as you may not know who is allowing feedback to occur and you need to understand people tend not to know about preferences when they seem 'hidden'.  Even the 2% are important (I'm sure your comment was not meant to be preceived otherwise) and it's still represents a huge number of people using Thunderbird. 

Please provide the following to find a permanent solution and fix this age old bug.
1. create the preference to choose whether  unread mail should be auto marked as deleted upon deletion.
2. Fix the 'Undo deleted message' to restore the 'unread' status, if that was the status prior to deletion.