I guess the 3px was more a rhetoric to drive home the more important point that design (UX and UI) matter. As has already been pointed out by someone in the this discussion, if a designer is asking you to more "3px", it is to align that element with other stuff on that page.
The larger point that it lends credibility to your product is mostly overlooked. I have seen in my consulting experience that taking care of small UX flow and info flow issues has led to veritable gains by companies.
Going by the discussion, it seems there is a good opportunity in the space of "engineering-design collaboration" :)
Personally (I don't speak for all devs, although some people on HN certainly seem to think they do...), the issue I have is that I rarely receive a response as clear cut as the one you propose.
"if a designer is asking you to more "3px", it is to align that element with other stuff on that page."
If they want elements aligned, or snapped to a grid, or whatever - sure, there is justification there. It's when I'm handed design changes with no justification that I get riled.
But yeah, at the end of the day engineers and designers really need to have a few more beers together.
The larger point that it lends credibility to your product is mostly overlooked. I have seen in my consulting experience that taking care of small UX flow and info flow issues has led to veritable gains by companies.
Going by the discussion, it seems there is a good opportunity in the space of "engineering-design collaboration" :)