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.