Different bits of the UI don't work on different mobile device platforms, not least as there is no dedicated 'mobile DaniWeb' interface. So, for example, anything Flash powered doesn't work on an iOS device.
The only browser that works properly with the ribbon/wysyiwg editor on my HTC Android is Firefox, but AFAIK, there's no Firefox available for iPad. Other browsers just show a plain textbox.
If you know the markup codes, just enter them manually. So you should be able to add bold/italic/code/inline code/quote/list items/headings/subheadings easily. The tricky one is link. Files is probably impossible, although I haven't looked into it.
You can easily add naked links, and the link syntax really isn't that hard to remember: [text](url). Files are impossible, but, in reality, just how intricate are your posts going to be on your mobile device?
I'd forgotten about Atomic on the iPad, it's been ages since I looked at that. Might be worth a quick re-download and taking another look then for those times I only have the pad with me when I need to do DaniWeb stuff.