Sorry. When there is huge amounts of activity in my absence, I usually read through the entire thread first, to make sure any comments I might make have not already been discussed and beaten to death.
So I copy and paste things that require replying into a text editor, preserving the original post number.
I then reference that number at the top of any post I make that does not automatically link back to the proper post. I am not about to dig back three or 4 pages to makes sure the linking all makes sense. I reference the number, so anyone can find it.
SD
When you find an old post needing your reply, you could right-click its "Post Reply" link and select "Open in New Window" from the popup menu (or, however your browser accomplishes it). The new window would have the triple benefit of negating any need for such digging, preserving your place in the old window and staging all the replies you wanted to post.
Just passing along a helpful hint, without denying my selfish motive.