>>> ... But if we click on
view/reply online, there should not be a reply box
automatically opened. We can do that for ourselves once
online by clicking the reply button. The problem is ... in the
automatic opening of the reply form... <<<
Yes, the "View/Reply Online" link in the footer behaves differently in group digest*** emails vs group individual emails; the former will automatically open the reply box, the latter will not; i.e. the former includes the ?reply=1 parameter in the link, the latter does not. So in the former case, any click on most all other options on the thread/topic page except the red Discard (draft) button will result in a saved blank message body draft.
The other two footer reply links behave the same, it's only this link that's different between the two. I don't know what's the intent behind this difference, but IMO it should work the same on both.
*** (I only tested the Full-Feature digest, not sure if it also does the same on the plain or daily summary emails)