I always thought carbon fibre paste was to help prevent carbon parts slipping in whatever they were clamped in. Now I read a post on Bicycle Ambulance that suggested the paste is to prevent the carbon seizing to metal.
Which is correct? Or are they both correct?

both. Acts as a corrosion barrier and an anti-slip.

Primarily an anti-slip, but does help prevent galvanic reactions between carbon and aluminium alloy. Something which I neglected with my alloy seatpost in carbon frame and it bonded. Took a hell of a lot of effort, tools, vice, plus various liquids to try to unbond it. Almost was going to cut the post but eventually got it out. Now I never leave the post in the frame at home. I do apply carbon paste but most of it is pushed off by pushing the post into the frame.

Ps the paste is recommended by some manufacturers even just for metal to metal. Just reduces torque required on clamping surfaces if it’s likely to slip.

Looks like I’ll be off to Revel’s in BSE tomorrow morning then!