That looks nice and gets rid of the confusion over number like "1,234" and "1.234". In the US, the former is the integer 1234 and the later is the rational number 1234/1000. In Germany or France, these would be the other way around. In SI, "1.234" and "1,234" would both be 1234/1000, and the integer 1234 would be "1 234" with the space there being a thin space.
Unfortunately, HN does not support THIN SPACE as far as I can tell.
Reddit is a little better. You can enter it in a comment and it will be correctly saved with the comment and it will display correctly in the browser. As long as you don't need to make any edits to your comment afterwards, it is fine.
If you edit the comment thin spaces are converted to regular spaces when it loads the editing widget, so unless you go through and put all the thin spaces back you will lose them when you save.