Why can't I search/filter on display names?

Question

See Question. Yes, it's 'display names', so I guess you can only see them on the display while thunderbird pretends to not know them really.
Still this is a less useful non-feature which annoys me a lot.

Answer 1

Display name:
is useful in identifying emails from specific people like family and friends.
It is more informal.
The shortened format means the 'From' column header does not need to be so wide - especially if these emails have been filtered to suitable folders.
for example: it is more user friendly to see FROM Mum instead of the long email address and many peopke do not always send emails showing their name.
However, like many things, you are not obligued to use it in the contact properties.
Regarding searching:
It depends upon how you are doing it. there are different search methods and each will search in a slightly different way.
If using 'Quick Filter Bar' then it does not search on Display name as those options are not available. It searches on Sender , Recipient, Subject and Body. But if the display name happens to be used in the body content then it will display.
If using global search then it does search on a display name.
Enter the display name in the search eg: Mum and select the Mum and email address option from the drop down offered.
It will show display name and email address, so you can select the search parameters.
If using this method:
Edit > Find > Search messages
This method searches on specific fields/headers and therefore will not search on a display name.
So I would recommend you try using the global search option if searching by a specific display name.