This column display in the folder pane is useful for users of Azure DevOps because the email notifications sent for check-ins come from the service managing Azure Devops and the developer that performed the check-in is only listed in the ReplyTo field of the email header. Without seeing this in the folder list view, you don't know who did the check-in without reading the email. It's also not searchable or filterable when looking for check-ins made by a specific developer.
This was never supported natively. I had written an extension to display it, but that became obsolete with Thunderbird updates. The ColumnWizard extension supported it for a while, but it also became obsolete and hasn't been updated. This is automatically supported in Outlook.
Seeing as the Reply-To header field is well defined, I don't see why it's not supported in the same way as the other email header fields such as From, To, Date, Subject, etc.
This is not a "big thing", but it is an annoyance and one of those things that can prevent adoption in enterprises.
It would be great if this could be considered. Thanks.