When someone works with some section/drawing I unfortunately can't add anything there... I even can't measure anything in that window (using lines for example). The only way is to copy section to my workspace and find out the dimensions I need there. But it doesn't seem to be the right way.
I think that sharing section/drawing workspace using layers (same way as floors) surely can improve teamwork process, especially with complex sections
1) Yes, you can measure things there. Just stop using the line tool to do it. The User Origin is your friend.
2) That's the point. You should NOT be able to add something to a section when someone else has it. The same goes for the Detail window. Can you imagine the chaos of people working THAT closely on top of one another? It's bad enough in plans when people try to split text and dimension layers and not overlap their printed work.