> Did you switch from two spaces to one space while writing in a text editor using monospace font too?
Yes, I switched to one space no matter what, but my use of monospaced fonts was rare back then. Even today I use only one space after periods, even when using monospace fonts. HN is an interesting case: The input field in comments is (I think?) monospace, but the output of posts is Verdana, which is not monospace.
Did you switch from two spaces to one space while writing in a text editor using monospace font too?