Ah, I have been looking for this comment. Finally someone else who does this! It doesn't just show me where my current spot to start from is; it prevents me from wasting time re-reading any text that I have already read. Even though this is my most common method, I occasionally use the mouse cursor (without selecting) to keep my place instead, particularly at the bottom of a page where I can no longer scroll down.
This is my method too. It also means that if I am interrupted I don't have to do anything to keep my place, although I still sometimes select text if I want to keep something above it on screen for context.
