Am I missing a trick or is that not implemented?

It's not implemented. Using the [code] blocks will at least retain the space formatting for indentation, but there's no syntax highlighting.

I wish we had syntax highlighting again.
It seems quite easy to implement with Highlight.js https://github.com/highlightjs/highlight.js

+1

It'd be easier to write an esoTalk plugin using the php Xojo syntax highlighter class that already exists.

I believe that syntax colouring will encourage more people to use the code tags.