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.
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.
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.