No, I didn't forget — browsers strip out the extra space, and I wasn't going to take the time to type in the HTML code ( ) to get an extra space (and HN seems to escape such codes in any case).

Yes, I'm a two-spaces person, because:

A. These days, readers are busy; they tend to scan text instead of leisurely contemplating and savoring each word.

B. The extra space after the period (or the full stop, if you prefer) helps the scanning reader to discern more quickly where one sentence ends and the next begins.

The Two-Space Rule is merely one corollary of The Cardinal Rule of Writing, which is: Serve The Reader.

(Another such corollary is: Short, Single-Subject Paragraphs.)