251550 was originally a d-i bug which after lot of analysis turned out
to be a console-tools bug.
This is the "d-i freezes when entenring high ASCII characters" bug.
Denis Barbier spotted the problem, provided a patch, and Alastair
integrated it in console-tools.
IIRC, the same patch has to be applied to kbd-chooser's loadkeys. I
guess Alastair will make the change in the currently unrelease 0.55
version.
My opinion is that this should make its way into testing as soon as a
few days sid_d-i tests will have proven it does not break the general
keyboard handling.