I see that there are 138 people online. Any way of seeing who they are?
You cannot see a list of everyone online. Also, keep in mind this is both guests and members. However, if you go to a users profile, it will say 'online' in green next to their username if they are online. Note that there is a preference 'display online status'. If this is set to 'no', then you will not appear online, even when you actually are.
And what is "fit to post"?
If someone posts a really long post, or a huge image, for example, It will appear cut off, and there will be scroll bars to view the entire thing. If you click 'fit to post' it will remove the scrollbars, and instead expand the box to the correct size to see everything.