Mastodon is compatible with "rich text" such as underlining, bold, italics, strikethrough, blockquotes, headers etc, and will display these correctly if a post uses them.

BUT... although it displays it, standard Mastodon doesn't let you create posts with rich text.

To create rich text posts you must use a fork of Mastodon such as Glitch, or a totally different Fediverse platform such as Friendica, Sharkey etc.

Lots more info about this topic at:

➡️ fedi.tips/is-mastodon-compatib…

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Is Mastodon compatible with rich text formatting such as Markdown? | Fedi.Tips – An Unofficial Guide to Mastodon and the Fediverse

An unofficial guide to using Mastodon and the Fediverse

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