Over 25 years in tech, I've hired many dozen developers. Only maybe 3-4 of the candidates I've given offers to in that time have tried negotiating.
I've never given an offer where there wouldn't be at least some room for us to negotiate.
Meanwhile I always negotiate when I receive offers, and have usually ended up with substantial increases over the initial offer.
That was 15 years ago, people didn't talk about this stuff as much back then, and hopefully I'm wiser now.
Next time I have a salary negotiation, if ever, I'm definitely going to scour HN for advice and read some books.
I’ve hired many engineers. Neither myself, nor any cofounder has been insulted or angry by a counter-offer. Sometimes we said to ourselves “this is kinda high for someone at their experience level” and held firm or met in the middle, but most of the time if you ask you’ll squeeze at least 5K more out of it even if your counter was 30K higher than the offer.
The closest I've seen was someone with wildly out of line expectations (a developer who asked for basically the whole employee option pool to himself). Even then we gave a counter-offer (that he declined).
Personally I'd see it as a sign they're not someone I'd want to work for.
If someone takes it as some perceived slight that you've asked for a higher amount, then consider they'd probably be equally offended if you asked for a raise down the road, and then you'd be in a bad spot...
Of course being able to not worry about being turned down is a luxury we can't always afford.
(Also, I have at times thought I massively overshot, and kicked myself because they immediately accepted; you'd be surprised how much of an increase you can ask for sometimes)