Subject: bug#20592: the `display' property messes the `face' properties after `concat'

From: Stefan Monnier <[email-masked]>
Date: Mon, 18 May 2015 21:20:05 -0400

> The behavior you observe is because the ':eval' construct expects to
> produce a single string with either the same common face spec on all
> of its characters, or no faces at all.  You cannot use ':eval' to
> produce a string that has more than one face spec on its different
> characters; if you do, only the face spec of the first character of
> the string will be honored.

IIUC, this is the bug that needs to be fixed.
Or is there a reason to consider this as a feature?

        Stefan