After upgrading to WordPress 5.7, the script admin of the forum let users know that from this version it was made a change for empty lines to be shown, resulting in a huge gap on some lines (see an example in the tweet).
While they haven’t clearly explained why this decision, here’s a simple fix to it.

In your theme style.css or the Additional CSS under Appearance > Customize, add this simple line

p:empty:before{content: none!important;}

And that’s all you’ll need to do.