Help adding custom html/CSS to post based on tags

[Timps]

Hey all,
I'm helping someone set up a new community for a not for profit and they'll need some custom functionality to hit their goals.

Can anyone point me in the right direction on how to use a plugin etc to add in html/css if a post or reply has a specific tag.

Short version is: People will be discussing different things and the org wants to allow certain conversations but to auto add in a disclaimer/change the post format a little for specific post tags.

IE: If the post has the tag: "marvel" on it, it'd show a div/text at the bottom of the post/reply saying "This person loves marvel".

New to NodeBB, not entirely new to everything else.