[dreamcompiler]

Extra space after periods is never correct with proportionally-spaced fonts, which is why all browsers remove it by default.

Two spaces after periods is a kludge invented for typewriters that had monospaced fonts and touch typing teachers need to stop teaching it in the modern era where most writing uses proportional fonts.

[dkga]

Curiously, it‘s also a tell-tale sign that a North-American typed the text.

[FabHK]

Just as a space before colons or exclamation marks is a sign that someone francophone typed it.

[dkga]

Indeed - especially the space before colons and semi-colons. The space before exclamation marks sometimes happens in informal typing amongst Brazilians. But never the space before colons/semi-colons.