You can, but maybe you shouldn't. Given that this post is in the fediverse community, I don't feel too bad about mentioning that Lemmy is part of a federated network with PieFed and MBIN (I try not to bollock on too much about the platform I happen to be using).

In the ActivityPub JSON for this post, there is no indication that this field contains MarkDown. If anything, it says the opposite, it says it contains HTML. It's therefore not unreasonable for other platforms to render it as such.

Given this, and the poor support for mobile clients indicated in the comments, and the fact that it's only a subset of MarkDown tags, but include ones that aren't part of CommonMark standard, I'd argue that it's not necessarily a good idea.

[–] fmstrat@lemmy.nowsci.com 4 points 8 hours ago (1 children)

Markdown is plain text, so it's fine to go in the field. It's also fine for apps to allow OP's post to look like garbage because there's no requirement for support.

[–] andrew_s@piefed.social 2 points 5 hours ago (1 children)

A comment here distinguishes between the 'plain text' that's allowed by the spec, and MarkDown as a markup language (it's confusingly named, I guess, but that's what Wikipedia categorises it as too)

[–] fmstrat@lemmy.nowsci.com 3 points 5 hours ago

Oh yea, I just mean that all markdown characters are ASCII, and thus allowed in a plain text field. 😉

[–] p03locke@lemmy.dbzer0.com 6 points 1 day ago

Also, this gives me real text-on-image-in-Facebook-post-just-to-get-noticed vibes.

If everybody can use Markdown in their post titles, then everybody will use Markdown in their post titles, until it's a mess of colors, bold, and italics.

[–] flamingos@feddit.uk 23 points 1 day ago (1 children)

In the ActivityPub JSON for this post, there is no indication that this field contains MarkDown. If anything, it says the opposite, it says it contains HTML. It’s therefore not unreasonable for other platforms to render it as such.

Actually, the name property is explicitly plain text, it shouldn't contain any type of markup, whether that be markdown or HTML.

[–] andrew_s@piefed.social 7 points 1 day ago (1 children)

Oh, wow. Thanks.

For clarity, I wasn't intending to say that PieFed treats that field as HTML (it treats it as text), I just meant that if you were looking at that JSON, and being a bit lazy like me and not looking at specs, then it wouldn't be unreasonable to assume that the 'mediaType' field also refers to 'name' (rather than a 'content' field which this post doesn't happen to have).

Anyway, this seems to be even more reason why MD shouldn't be put in titles, and front-ends shouldn't be encouraging the practise by rendering it.

[–] kat@orbi.camp 3 points 1 day ago

Eh, I'll probably use italics tho, just like I did * in reddit.

[–] nutomic@lemmy.ml 3 points 1 day ago

The Lemmy backend doesnt treat this field as markdown, if you look at the Activitypub data (curl -H "Accept: application/activity+json" https://lemmy.world/post/24241974 | jq) the title is federated as plaintext. Only lemmy-ui decides to render it as markdown for some reason.

[–] AA5B@lemmy.world 4 points 1 day ago (1 children)

In the ActivityPub JSON for this post, there is no indication that this field contains MarkDown. …. it says it contains HTML

This seems like a bug. Regardless of what clients may support, the json ought to accurately describe fields

[–] andrew_s@piefed.social 9 points 1 day ago

Another commenter (who's contributed code to Lemmy) pointed to a link that provides the specification for that field: "A simple, human-readable, plain-text name for the object. HTML markup MUST NOT be included."

So in this case, it's more that the JSON looks a bit ambiguous: 'mediaType' is only referring to the format of the text in a post's body, but - unlike me - you'd also need to be aware of the spec to know that it doesn't apply to the title.

[–] schnurrito@discuss.tchncs.de 1 points 1 day ago (2 children)

Do you know a way to see the ActivityPub JSON for fediverse objects?

[–] BentiGorlich@gehirneimer.de 6 points 1 day ago

you can use https://browser.pub/ I like it very much for that use case :)

[–] andrew_s@piefed.social 5 points 1 day ago (1 children)

Yes - it's easy to do from a command line. For this post, it would be:

curl --header 'accept: application/activity+json' --location https://lemmy.world/post/24241974 | jq .

it looks like

{  
  "@context": [  
    "https://join-lemmy.org/context.json",  
    "https://www.w3.org/ns/activitystreams"  
  ],  
  "type": "Page",  
  "id": "https://lemmy.world/post/24241974",  
  "attributedTo": "https://lemmy.world/u/amon",  
  "to": [  
    "https://lemmy.world/c/fediverse",  
    "https://www.w3.org/ns/activitystreams#Public"  
  ],  
  "name": "By the way, you can have `Markdown` in Lemmy post titles",  
  "cc": [],  
  "mediaType": "text/html",  
  "attachment": [],  
  "commentsEnabled": true,  
  "sensitive": false,  
  "published": "2025-01-13T20:48:50.824942Z",  
  "language": {  
    "identifier": "en",  
    "name": "English"  
  },  
  "audience": "https://lemmy.world/c/fediverse"  
}

[–] schnurrito@discuss.tchncs.de 1 points 1 day ago

Thanks, will try that out