BuddyPress.org

To be a bit clearer, here’s the info from the style.css file on making a child theme:
Instead, please read this codex page on how to build a BuddyPress child theme:

https://codex.buddypress.org/how-to-guides/building-a-buddypress-child-theme/

And if you decide not to make a child theme, make sure you put any modified styling info after these lines:

/***
* The default theme styles.
*/
@import url( _inc/css/default.css );

/***
* The admin bar default styles
*/
@import url( _inc/css/adminbar.css );