@anon8189768, it seemed appropriate to reply in here. 
The way you did it was fine. 
You thought there was a bigger conversation to be had, and that it would take it off-topic if you had it there. And you included a link to the original post, which joined it all up. 
There is a button that will do that for you called ‘Reply as linked topic’, and that pretty much does exactly as you’ve done. You can find that in your reply window, above the format bar in the very top left. If you tap the swoosh arrow it will bring up the option ‘reply to topic’, or ‘reply as linked topic’ (the menu is a bit squiffy, but it’s the + symbol). If you tap that it’ll convert your window into a ‘create topic’ one, and insert something like:
Continuing the discussion from The Sandbox:
at the top, that links to the post you’re replying to.
It’s also in the timestamp menu in the top right of every post.
I’m not sure I’ve seen anyone actually use it yet though.