[saagarjha]

Except in Slack, which somehow interprets this to be italics.

[floatingatoll]

They were always meant for emphasis, which takes on variable definitions over time. Terminals were bad at italics due to character box layouts and so the literary approach of emphasis through italics mutated into emphasis through underlines. Now that we’re all free of monospaced terminal grids, it looks like we’re drifting back to emphasis through italics.

[fao_]

Italics were still used though.

Like /this/.

[kevin_thibedeau]

Underlining was a substitute for italics before everyone had fancy word processors.

[naikrovek]

Markdown started that in general. There's no way to underline something in Markdown; underlining just isn't supported.