As it is unclear when the updated dasboard will be available, it would be nice if also the current dashboard would respected local settings for separators.
That's the reason why I wrote already in the current dashboard. I think it might be easier and faster to change the current implementation than to attract new developerd. See this post
I agree.
A lot of users might use pre-made images (of raspbian, or other distribution) which might have different local settings than their clients they use to access the Web GUI.
Yes. This is also why we're already doing the timestamp conversion client-side. This has the nice consequence, that you are, e.g., seeing your Pi-hole's statistics in the local time of the country your currently visiting (assuming your're using your Pi-hole over VPN). At the same time, my wife was able to see the statistics in her local time at home - on the other side of the planet.