Yea, it’s bad practice 
.. But we still have such code in the core templates. The process to get rid of it is slow, because of our backwards compatibility rules. We don’t want to break older stuff accidentally.
Because … It’s actually a bit more complex then that. As I wrote at: Hackability of default triggers - "Buttons" · Issue #4272 · TiddlyWiki/TiddlyWiki5 · GitHub
The button can look different:
\define ext-actions() .... <$button message="tm-close-tiddler" actions="ext-actions"> <$action-xxxxx aaa bbb ccc> </$button>Now a UI button has 3 “actions”
- the “body” actions.
- The message
- the ext-actions
The button widget core code executes it in the order shown above.
body actions - message - ext-actions
I’m pretty sure, that I did “mis-use” that behaviour in one of my wikis. … So “just” move every action out of a body if it has a message may break some code.