PieFed v1.4 will have Stack Overflow-like functionality: the person who posted a question will be able to choose which of the replies are the answer, by clicking the green tick icon in the bottom left. Chosen answer(s) then have a highlight and a green tick at the top of them.
This is off by default - communities have a checkbox on them that needs to be toggled to turn it on. So only some communities will have it.
To Lemmy instances, these questions and answers will look just like normal posts and comments, without the highlight and tick. So people using Lemmy will be able to contribute.
Designating which comment is an answer involves federating a new Activity:
{
"id": "https://piefed.social/activities/answer/hgb4iO4b8UAFRTn",
"type": "ChooseAnswer",
"actor": "https://piefed.socialz/u/rimu",
"object": "https://piefed.ngrok.app/comment/224",
"@context": ["https://www.w3.org/ns/activitystreams", "https://w3id.org/security/v1"],
"audience": "https://crust.piefed.social/c/linux_questions",
"to": ["https://www.w3.org/ns/activitystreams#Public"],
"cc": ["https://crust.piefed.social/c/linux_questions"]
}