Carol, you bring up a very good question. What exactly is "nitpicking"? And I suppose there are as many answers as there are readers and writers.
For the purposes of this poll, I'll give you my definition. Or perhaps, maybe it's easier if I tell you what I've always expected during the different stages of my writing a story.
When I write something and send it to my beta readers, I expect them to help me locate plot holes and call out any serious story and/or characterization issues. If they happen to notice a mis-spelling or grammatical error or type-O, I'm always thankful when they point it out. I like to have as close to a perfect copy as I can manage before posting to the boards.
When I post to the boards, my expectations of any feedback I receive are along the lines of general feelings/thoughts about the story, as well as pointing out plot issues, story problems and characterization mistakes. I also am glad for the added bonus of the vast intellect of the readers, appreciating very much when they point out stuff that I've gotten wrong on a factual level. For example, if I've had Martha undergo some medical procedure and have really botched it, I'm so thankful if DocJill will pipe up and say "No way. That could never happen."
What I define as "nitpicks" at that stage are when readers point out things like spelling errors or tiny grammatical issues (missing/extra comma, the like). This includes American English usage versus Other English usage, unless I'm trying to sound British and have gotten it all wrong or have totally misused some phrase. And while I certainly need to know that these problems are within the story and need to be fixed, it's when the feedback starts to revolve more around the type-Os than the story itself that I start to flinch.
Finally, in the last stage of story after I've sent it for GEing before archiving, that's when I expect the nitpicking to be at the very highest level. I want to know every mistake in the story so I can fix them.
Like I said, I'm sure others in this fandom would think that pointing out any story problem is nitpicking while others would think that no detail is too small to deserve critique. It's pretty a wide definition.
As for the question about my use of "expect", I'm not sure which context you mean (I'm growing daft in my old age

. When I read a story, I expect a fairly clean version, with the most minimal type-Os, spelling errors, etc. If I'm reading something and every other sentence contains a problem, I become too absorbed in the errors that I can no longer focus on the story and usually have to stop reading. If I'm reading a story with virtually no errors at all, when I stumble on one I usually just skim right over it. Does that answer your question??
Lynn