[PeterisP]

"the idea would be to hide data by using different amounts of spaces in text files, in the least significant bits of pixels in images, or in the access pattern to a certain service" is not appropriate for the claimed use case, i.e. activists in totalitarian regimes.

In such an environment, the traffic of suspected activists will be analyzed.

Assuming the kernels are open, it's possible to see in analysis of certain data that "amounts of spaces in text files, in the least significant bits of pixels in images, or in the access pattern to a certain service" have encoded information, even if the extracted information looks like random/encrypted data. At this point you don't have plausible deniability and rubber hose cryptoanalysis can be used.

Switching to new kernels happens too late since you don't know when they've identified a kernel until they start arresting people - it's not like they're simply going to block it immediately.

i.e., the described service is resistant to mass censorship and automated filtering, but these use cases actually need to be able to resist attribution and retaliation, which are quite different problems.