Thanks for all the responses.
My main point is that I want my e-mail client to be very transparent about "From" (as well as To:, Cc:, Date ...) I don't want any masquerading. For that, I've disabled "Abbreviated recipients" under Settings -> Message view. Why the sender (myself) remains abbreviated with that, it beats me.
While masquerading may work for some users, it is bad for others, who are more technical. (Also, in general, it can be bad for security reasons.{*})
So, besides being inconvenient (and surprising) to some users, it is also inconsistent in the intent. (Yes, I know, that option is for the recipients, while I am talking about the sender, but I am talking about the intent of behavior here.)
Besides (but this is really a secondary point), - Aquamail is inconsistent in how it shows the sender.
As in the example above, - for the messages sent from the "main" identity (i.e. the account itself), - it shows "From: User Name <user@domain.com>", not "From: [Account name]". (which is good!!!)
But, as described above, for additional identities, it is: "From: [Account name]/[Identity name]".
{*} E.g. the trend of programs (primarily under Windows) to hide file extensions yielded many exploits.
So, Kostya, would you please, kindly consider some way of making it possible to display the actual e-mail address in the header.
This post was sitting on my screen for 3 months.
Now, as you've added an option to make even more substitutions for addresses (from the contacts), -- all embellishments, maybe you can also satisfy the need for a "pure" display, of what is actually in the message?
Thank you!