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.