I have this question for years, don't ask me why I never asked or solved it. Therefore: big thanks for bringing up the issue.
IMO there should be an admin option to specify the decimal sign 0,01 or 0.01 and the separator for thousands 1.000 or 1,000 or 1 000 (empty too).
Attempt without core hack:
1. Create a layer plugin or use the advanced theme, i.e. edit the file qa-theme.php
2. Points are output in the user nav and in the user meta, and users pages, so we should catch those from the $this->content:
3. e.g. override the head script like that:
// access points from $content, change commas to dots of logged in user
Unfortunately, as I see now, maxjtechno is right. The value cannot be overriden. It is indeed set by the core.
Use Jquery: FIND all points occurences by its class names, and string-replace the char '.' with ','.
I really hope Scott can fix this. I reported the issue at github.