[account42]

Let's actually fix it:

  :root {
    font-size: 1rem;
  }

Done. Don't mess with the user's preferred font size. If you think some browsers have bad defaults, campaing to have them fixed instead of hardcoding incompatible hacks for each website.

[tln]

I'm not so sure..

There are good reasons to use different font sizes for body text depending on purpose. Hacker News' small fonts fit more comments on the page. A documentation site may benefit from fitting more text on the page. A spreadsheet benefits from even smaller text. The article is easier to read with larger fonts. I tried the article with your rule, it's just not as nice.

Then I changed around my "preferred font size" (chrome://settings/fonts -> Font Size). Blog responds just fine to it. Ironically many, many, many sites don't. It's actually so useless in general to change your default font size that browsers have a much more useful way of letting users have small or large text -- zoom levels.

[bee_rider]

All of your examples benefitted from smaller text. And the caveat is always that it has the be big enough to read. Therefore, just let the user set the size, they can set it to the smallest size they can read.