I totally agree with the need expressed in original comment/request along with the security concerns and I don't understand why all email systems don't display the full sender details everywhere possible (or at least have the option to do so if it's a question of space saving for some).
Apart from the security aspects and being able to see at a glance if the sending domain is as expected (instead of hovering or actually looking at an email), so many times I have people with similar names and/or use multiple email addreses and without the ability to quickly see the full details like e.g. "Display Name <name@domain.com> it makes life much more tedious, unsafe and prone to making mistakes (when sending or receiving).
I came here after experimenting with RoundCube again and found the full display possibility missing in the column showing my inbox contents. Additionally and similarly, because of the odd way newly used sent-to email addresses get added automatically to Collected Recipients they get assigned a display name that I didn't set (taken from the part before the @) which makes it very difficult to know or see the real details which very strangely gets that artificial shortened Display Name used when sending new emails out to that contact (and I can't tell who it's actually to especially if I might have several contacts called "Dave"). To edit/correct that, I have to move the Contact to Personal Addresses where I see nothing actually saved for the Display Name, press save and then it works as expected.
I use Thunderbird all the time normally with the full details showing using the "Full Address column" plugin but without that ability in RoundCube it makes my use of it unlikely. Shame, as otherwise Roundcube looks like it could be really useful at times.