[Vapormac]

Is the _underscores_ around words supposed to signify something? Or am I just using the wrong browser to view HN and it's not rendering or something. Sorry if this is an obtuse question I'm new here.

[tupac_speedrap]

It's a Reddit thing, it makes the text bold on there but people seem to use it on here by accident.

[epukaza]

It's older than that, gmail (also maybe MSN messenger?) used to have underscores italicize text, and asterisks would bold text.

[nitrogen]

Probably habit on the part of the OP from other markup languages, to show emphasis. HN uses asterisks * for italics/emphasis: https://news.ycombinator.com/formatdoc