I do not doubt that microaggression exists in human communication.
The problem is ambiguity exists in all the same places, so you can never be sure what is aggressive, wary, weirdly friendly, just weird, or nothing at all.
A recent paper on microaggression has this to say:
The microaggression concept has recently galvanized public discussion and spread to numerous college campuses and businesses. I argue that the microaggression research program (MRP) rests on five core premises, namely, that microaggressions (1) are operationalized with sufficient clarity and consensus to afford rigorous scientific investigation; (2) are interpreted negatively by most or all minority group members; (3) reflect implicitly prejudicial and implicitly aggressive motives; (4) can be validly assessed using only respondents’ subjective reports; and (5) exert an adverse impact on recipients’ mental health. A review of the literature reveals negligible support for all five suppositions. (Microaggressions: Strong Claims, Inadequate Evidence)
I think we can assume that intercultural interactions will often involve many prejudices and assumptions founded on cultural norms and that microaggression will sometimes be one of these. But that is very hard to study, quantify, and identify.
In public situations—jobs, organizations, many private settings—just follow public norms and forget about microaggression. Your looking for it will itself constitute a kind of microaggression.
In private, you can and should do something about all kinds of interpersonal micro ambiguities.
The way to do this is FIML practice.
I found the study cited above in this essay, Micro-aggression and Hyper-sensitivity, which discusses the study.
Signal networks should be conceived of as dynamic patterns that change over time.
A psychological example of this might be a short exchange between two people during which one person interprets a small signal coming from the other.
The signal might be a fleeting expression. The person who sees this signal is likely to interpret it and remember (weakly or strongly, for some period of time) what that interpretation is.
As something held in memory—short or long term—that interpretation of the fleeting expression has become both itself a signal and part of a signal network that is changing over time, changing in part due to that new signal.
Of great importance psychologically for both persons described above is the fact that neither knows how the other interpreted the fleeting expression or if it was interpreted or sent or received. Or remembered or for how long. And almost never do they know how to get that information.
This is a micro example of human communication as it happens in time.
If this micro signaling network is held in the mind and analyzed correctly by the two persons described above, much will be revealed to both of them about how their psychologies actually function in real life and real-time.
FIML practice is designed to get them to that point.