I agree, it would be great to see badges awarded to a certain post in its context, so that other users might feel motivated to get this badge as well. As an alternative, posts who got a badge could have its own class, so that they can be styled differently in the css.
Are there any plans to implement this? In general, I wish badges in Discourse were more prominent. I love the idea of rewarding desired behavior. If a post is that behavior, why not make the granting visible to everyone? It will encourage more of the behavior we want.
Add a staff note to the posts you assign badges for, it can link to the badge.
I feel this resolves the OP really cleanly and wonder if we should just have some way of doing this automatically by adding a checkbox. But a workaround exists now and is super clean.