@tallship Yes, it is a feature from GitHub Flavored Markdown
~~text~~ renders as <del>text</del>
@mario says Hubzilla will support this tag: https://hub.somaton.com/item/5d22eb3e-79eb-4e4e-9831-5aa269d70c4a
But people are also reporting that Fedilab doesn't display it correctly so I'm hesitant to enable this feature. The perceived meaning of the message can be very different without this piece of markup.