Show age warning more prominently at the top of posts

I visited a random topic and browsed through it and then decided to reply, to which I received this:

This happens often.

It’s true that the posts do have May '18 tags in light gray in various places, but, I’m sorry, that is not a good way to tell a reader “This is an old post”. If it was, then you wouldn’t show a large blue box with a large bold black heading and 2 paragraphs warning me that I shouldn’t reply to it.

Some newspapers actively add banners to the top of their old articles to warn readers about this…