Should I simply ignore it if authors assume that I'm male in their response to my review of their article? I received a response about a manuscript I reviewed earlier, and the authors write about the reviewer (i.e., me) and his concerns.  As a woman, I'm not so keen on this.

Obviously this isn't intentionally insulting or anything like that---it's a minor blip.  Nevertheless, it's a bit irksome, and the feminist in me is thinking that's not right; it's a microaggression (one of the everyday reminders that you don't belong here).

I could simply ignore it, but...

Question: Should I simply ignore it if authors assume that I'm male in their response to my review of their article?

There's no issues inside the manuscript: they thank the reviewers without using pronouns.

I'm particularly interested in if an editor would typically just groan and consider me a troublemaker for saying anything.  And probably not pass the message on to the authors anyway.
As a reviewer, you are supposed to comment on academic value and scientific correctness of the manuscript.

As a woman, you feel unhappy about authors not guessing a correct pronoun for you and not using an appropriate gender-neutral pronoun. 

It seems that the issue has nothing to do with the manuscript and hence you are not reacting with your reviewer hat on. You are considering your response based on your role as woman/feminist/activist &mdash; but not as a reviewer. You are not reviewing the paper, you are reviewing author's communicative behaviour.

As long as you make it clear that you are not commenting as as reviewer of a manuscript, I think you can make this remark to the editor.