If you look at the right hand side of a post, there is a # and a number. When you need to refer, right lick on that number and "Open link in another tab or window". It will open that thread at that post and you can navigate from there.
Most browsers clobber existing data when you open another window because your opening another copy of the page
If your planning a LONG post, compose it in a word processor.
I have a related issue that seems to have no solution. When I'm composing a reply, my fingers appear to slip sometimes and the post disappears. I haven't figured out what really happens with my fumbly fingers.