Got a response to my GitHub suggestion, which I'll copy here:
It's up to the theme to determine what the .deleted class does, in persona it just adds opacity: 0.3 to the content element.
Unprivileged users don't see the contents of deleted posts this is separate from the styling. So you could override the css and remove the opacity but regular users still won't see the content of deleted posts.
It is very simple for a theme to add additional messaging to posts if they are deleted. ie
{{{ if posts.deleted }}}
this post is deleted
{{{ end }}}
This can be added anywhere in the post.tpl and it will show a message for deleted posts.