I don’t know if this is a bug or just an annoyance.
I use Bricks Builder on a Mac running macOS with the primary language set to German. The website I am building is in English and uses Wordpress with the English locale. The thousands separator in the Counter element of Bricks is still the German dot, not the English comma.
I would expect that Bricks uses the English thousands separator on sites, where the site language in the Wordpress General Settings is set to “English (United States)”.
Alternatively, or maybe even better would be a setting in the Counter element or in the Theme Styles.
You are right that the comma is more commonly used than the period in English-speaking countries. Nevertheless, both are valid, recognized, and readable.
Since this is not a bug, I am moving the post to Feature Requests.