Basically what I wanted was a way to just copy & paste the website capsule description. At the end, I got it to work fairly well, considering the limitations. But, I implemented it as 32 bit shell extensions. As soon as it's finalized, 64 bit comes along and obsoletes it. I coded it more to learn how to do the extensions rather than to get the actual utility. Probably why it wasn't popular.
Of course the weakness of the Tooltip popup is, you don't remember which ones have comments, so you hover the mouse waiting for something to happen. It's a flawed design.
btw on the remembering last line caret position, it occurs to me you might want to look at some of the Scite based editors. Seems to me either or both of Scite4AutoIt3 or Scite4ahk remembers the position in the file when you go back. Could be only for the last file edited though. I'm not sure.