Ethanol makes a big difference in turbocharged cars, even in small amounts, that's why one of the best ways to check for fuel-related knock is adding a few gallons of E85. If your knock goes away then either you need better fuel or a softer tune and if it doesn't then you probably have another issue altogether. Obviously that's under the assumption that you're monitoring ignition correction often and knock 'suddenly' appears.
Seeing "some" knock is normal and expected though, correct? As an example, yesterday I saw a negative ignition correction and a 1/0 knock count while engine braking from a 4th gear run up to 6k rpms. This isn't datalogged, but monitored on my AP while watching cylinder 1.
While datalogging and doing a 2500 rpm WOT pull to 6500, there are no negative ignition corrections and my positive corrections all fall in line with one another without the AP registering any knock 0/0.
When I was a mx5 owner pre FiST, the tuners on Miata.net would say that seeing some knock was normal and expected, and I guess that my question boils down to what could be causing knock to register in my car or any other while engine braking?
What my AP read yesterday after I got home from a fun run
Peak Boost 25.1 psi
Cylinder 1 ignition correction -1.0/1.13
Cylinder 1 knock count 1/0
Octane Adjust Ratio -1/-1
PS: I drove the car really hard yesterday afternoon, and I hadn't recently registered any negative corrections or knock prior to running it like I did yesterday.