While I don't know the scientific reasonings for why a turbo begins to glow (other than the fact of extreme heat), I can say that there are SEVERAL cars I know of that have glowing turbo(s) and/or exhaust manifolds.
For example, a 1200awhp Skyline on the dyno, completely glowing turbo's and exhaust manifolds look like there's flowing lava beneath the housings.
or, a Civic HB Turbo w/ the hotside glowing bright red after doing acouple hard interstate pulls.
or, a 92 1st Gen GSX with a mildly glowing exhaust manifold and BRIGHT glowing turbo after boosting across town randomly.
^^All random things, at random times, and all different scenario's.
So, if the conclusion to having a glowing turbo means you have a boost leak... then I am very confused at this point. :icon_conf There has GOT to be more to it.
On a second note, no, it's not NORMAL.
Jeff