i watched so you don't have to ...
desperate for some hard sci fi, i am marathoning Star Trek:Enterprise
if you remember the DS9 episode Trials and Tribble-ations time travel episode (DS9 spliced with ST:OS Trouble with Tribbles)
Worf is asked about the lack of forhead ridges on the 'old style' klingons?
and his reply is ' we don't like to talk about it"
Season 4 Episodes 15 & 16 - the Klingons stole the genetic tech for 'super humans' (Khan) and used it to make their own 'Augmented' Klingons..
but it turned into a virus that a dissolved the brows and then killed the infected. Needless to say the Enterprise Doctor cured them but Millions of Klingons lost their brow ridges and it would be passed on to their heirs. I am assuming plastic surgery would be popular on Klingon Homeworld.
(BTW Dr Flox keeps a tribble...he feeds the resulting tribbles to one of his many pets)
Just learned that figured i'd share..i know you have been waiting for that answer for years..
anyone ever discover something similar?