Should we show user information for deactivated accounts?

I am building a dating website, which contains a messaging system. On each conversation I display the username and avatar image of the person you are talking to.

Users have the ability, at any time to deactivate their account. That is for example if they have found someone and are no longer looking, but don't want to permanently delete their account in case they want to start looking again in the future. Whilst their account is deactivated, their profile no longer appears in the search results and their profile cannot be accessed via its URL.

My question is, what should happen on the conversations that they are participating in whilst their account is deactivated?

Should I replace the user's username with a placeholder like (unknown user) and likewise replace their avatar with a placeholder image?

OR should I keep their username and avatar displayed but show a message saying Sorry, this user is no longer available?

Of course I could just make the conversation disappear, but I don't really want to do this, in case the user has sent an abusive message before deactivating their account - I would like the recipient to be able to report the message.