It is pretty much trial and error to get the timing down. The end result of this is a chest that contains random loot... and maybe a set piece or something in DKS / D2:DC.
In D2:ED it took me a few tries, but with good timing, and starting off facing where the platforms will be, it was possible to jump up both before they disappear. There is a button or pressure plate on the second platform which will fix them in place and cause a chest to appear on the ground near the entrance of the room, which you will need to drop off the platform quickly in order to reach before it disappears. In D2:ED it had a potentially decent legendary quality random item (good enough to try a few times for, but not enough to worry about if you can not get it with a reasonable effort). In DKS the platforms were changes slightly (I don't recall how, just that I needed to change my approach a bit) and I think something may have been added to the chest (or maybe I just recall it being better because I got a slight helmet upgrade from it, whereas in D2:ED I think I got a couple pieces of equipment I ended up selling).
When you edit a post, there is a delete button beside the change and preview buttons. If you delete a lone post that nobody has replied to, it will delete the topic.