Do accelerated charges radiate or not?
It depends. A falling charged particle doesn't radiate. Nor does a charged particle accelerating because of a static electric field. Cyclotron radiation and synchrotron radiation are associated with acceleration due to a magnetic field.
This questions has been asked all over the net (here included) but I can't find a satisfactory answer or discussion. Some say it does not radiate if the acceleration is caused by a uniform gravity field.
A falling charge does not radiate. It doesn't matter whether the gravitational field is uniform. The particle is in free fall, and the principle of equivalence says standing on the ground is like accelerating through space. But note that a charged particle sitting on the ground doesn't radiate either. It only radiates when it stops falling because it hits the ground. Compare this with what happens to the electron when it's attracted to the proton to form a hydrogen atom.
Some even say that it radiates in linear accelerators because of our imperfect technology.
Can you give me a reference for that? See this: "While it is possible to accelerate charged particles using electrostatic fields, like in a Cockcroft-Walton voltage multiplier, this method has limits given by electrical breakdown at high voltages. Furthermore, due to electrostatic fields being conservative, the maximum voltage limits the kinetic energy that is applicable to the particles. To circumvent this problem, linear particle accelerators operate using time-varying fields..."
All this comes from university member (at least they claim to be). My head is spinning. I always thought (from CED) that any kind of acceleration causes the charge to radiate and lose energy
Not any kind, and not gravitational falling-down acceleration. That converts potential energy, which is mass-energy, which is internal kinetic energy, into external kinetic energy. It doesn't radiate it away whilst the particle is falling. In similar vein falling down doesn't hurt a man. It's the sudden cessation of falling down that causes his teeth to radiate across the pavement.
not that I say that this is the case, but the equivalence principle of relativity never crossed my mind while thinking about this puzzle. Today it did.
It shouldn't be a puzzle. IMHO it's only a puzzle because somebody has oversimplified some teaching. Or maybe confused two different fields of physics.
Can someone here give some good, kind of fresh, references (no ArXiV please!) or alternatively, try to explain better than what others have done?
I'm not sure I can. Have a look at this. And who's telling you that falling charged particles radiate. They don't. If they did Einstein's general relativity would be wrong, and it isn't. Instead it's one of the best-tested theories we've got. See The Confrontation between General Relativity and Experiment by Clifford M Will.