I think it depends on the client you use, it's not standardized

Gotcha. Anything client specific for #amethyst I wonder?

NIP-01 covers basic requirements for clients to present formatting characters (line breaks, double quotes etc.). NIP-23 covers long form which allows for Markdown styling. As was mentioned it is up to your client how these things look to you. For other clients you cannot assume the same. For your example in Damus I just see a text string with double asterisks either side of the words.

Maybe I'm missing it, but I don't see anything about presentation in NIP-01. Only mentions of line breaks, for example are in the context of how to properly structure events for signing and verification.

I was mistaken, it's in the description if of kind 1, text notes, and it specifically says it should be plaintext and further says "Content that must be parsed, such as Markdown and HTML, should not be used." So clients shouldn't even be doing any formatting. Pretty sure long form content is supposed to get markdown formatting by definition, though, so perhaps the client is publishing as long form to get markdown support.

Thanks to both of you for the insight.

I wouldn't recommend using client specific formatting. I know it's tempting, but it's not going to look the way you want to a large portion of people who see it since they'll probably be on other clients. Wherever possible, it's best to use the universal standard, and if you can't for some reason, probably wanna mention what you're using instead, e.g. markdown instead of plaintext.

Certainly. I just happened to notice that #Amethyst had some support for it. So, curiosity led me to ask. I greatly appreciate the clarification here.