What are some other examples of artifactual communication?

Kayvon mentioned in lecture that there were examples of artifactual communication from other I/O operations, like when sending/receiving data to/from a network.

Echoing stao18's question, but more specifically - curious about what the most significant forms of artifactual communication people in networking or distributed systems fields think/worry about.

Separately - one subtlety that comes to mind here is that the OS may be swapping different kernel threads / user processes on and off the CPU. Even if one process takes good advantage of the cache, those benefits could get thrown out by the scheduler. (Thinking about, for ex, how CPUs have the concept of affinity / trying to schedule the same processes to the same CPUs).

Would something like hidden synchronization (for example, inter-thread communication in a parallel allocation system or atomicization of file I/O) be considered artefactual communication for the client of that system? All of these examples are pretty hardware-oriented, so was wondering what something like this would look like on the software side, if such exists at all.