Hillary Clinton’s acceptance speech at the Democratic National Convention was an emotional, historic moment for many. But some commentators also fixated on things like Clinton's voice, or whether she was smiling:

Instead of lecturing 2 citizens @HillaryClinton needs 2 have conversation w/us. Modulate voice. Tell stories. Set hopes. Smile #DNCinPHL — Steve Clemons (@SCClemons) July 29, 2016

Interesting to hear the women on @NPR talk about how awesome @HillaryClinton's speech was while the men are like meh and mention her voice — harper (@harper) July 29, 2016

Brit Hume - "She has a not so attractive voice" — Crowley Report (@crowleyreport) July 29, 2016

BBC presenter calls Hillary Clinton "shrill" https://t.co/l4UTCNag6o and.. this is why so any people switched to @Cspan — Jodi Jacobson (@jljacobson) July 29, 2016

Donald Trump also weighed in on Clinton's "very average scream":

Crooked Hillary Clinton made up facts about me, and "forgot" to mention the many problems of our country, in her very average scream! — Donald J. Trump (@realDonaldTrump) July 29, 2016

These kinds of comments made during the campaign have been a constant frustration for feminists, who say they are a sexist double standard. This time was no different:

Last week the Republican nominee yelled at us for over an hour but tomorrow we'll wake up to so many stories about Hillary's voice — delrayser (@delrayser) July 29, 2016

If you're a dude thinking of saying that Hillary should have smiled more, changed her tone, or moderated her voice in any way, REALLY DON'T. — Melissa McEwan (@Shakestweetz) July 29, 2016

We've seen these kinds of comments on cable news, and even after Clinton scored huge primary victories in Ohio and Florida:

Hillary shouting her speech. She has the floor; a more conversational tone might be better for connecting with folks at home — HowardKurtz (@HowardKurtz) March 16, 2016

Smile. You just had a big night. #PrimaryDay — Joe Scarborough (@JoeNBC) March 16, 2016

When women speak, people tend to mentally turn up the volume

Women, and women leaders in particular, often get criticized more for how they say something than for what they actually say. They have to walk a difficult line of being assertive but not too aggressive, likable but not too much of a pushover.

Even though women are interrupted more often and talk less than men, people still think women talk more. People get annoyed by verbal tics like "vocal fry" and "upspeak" when women use them, but often don't even notice it when men do.

The same mental amplification process makes people see an assertive woman as "aggressive," which gets in the way of women's personal and professional advancement. Women are much more likely to be perceived as "abrasive" and get negative performance reviews as a result — which puts them in a double bind when they try to "lean in" and assertively negotiate salaries.

These kinds of implicit biases are sexist, but having them doesn't make someone "a sexist" — or if it does, it makes all of us sexists. It doesn't matter how smart you are or whether you are a man or a woman; everyone has some implicit biases against women.

And that may be one reason why this is the first time a woman has ever won a major party's nomination.

Watch: Hillary Clinton’s acceptance speech