>>>On that left side menu, how do you clear all you replies that you've read? Not the Private ones, the ones under the Replies heading.
>>
>>Click on this reply, it will open it, then click on Remove option.
>>
>>Or open all your replies from the top toolbar menu (the button to see all your replies) and select the ones you want to move to Read.
>
>How can I just mark a message as Read while I am reading it?
>
>I usually just click on a message in the Sidebar under the Replies area (without actually opening up the entire Replies page), and it shows it to me, but there is no way to mark it read right then. There are other icons in the toolbar when viewing a message by the method, like Save and Delete, so why not one for Mark as Read?

In your PUTM account setup you can check option to move your replies into read as soon as you read them.

I personally rarely delete replies or move them to read, so I have 17333 replies in unread at the moment.