Yes, that’s good in Discourse but I’m talking about posting links to Discourse topics in Facebook, Twitter and so on.
They don’t do what Discourse does, they show a blank image unless you put those tags. Try it. But once we put those meta tags, now they override everything.
I’m just saying, it would be a great idea for forums to have a field for a default image that is used when posting, but overridden when the topic has a better image. (And if you really want to get fancy, then topics can have one.)
The meta tags I’m talking about are og:image and twitter:card