I was adding a book to Calibre yesterday and was wishing it had a second comments field. I had gotten into the habit of adding notes to myself about the book source and conversion steps inside the comments field, but it wasn't an ideal thing to do as it cluttered up the field. So I wanted to separate personal notes from the little book synopsis that usually goes there. I figured I'd come here and post an enhancement request to get a second comments field added to Calibre.
Well before I did, I started poking around Calibre and noticed the custom metadata tab which I had never looked at before. Through further research into custom metadata, I discovered much to my great delight that Calibre already let you add additional long notes fields! I knew you could add custom columns but figured they were limited to short text, yes/no, and check mark options. So now I've added two additional comments fields -- one to note the book source and any notable conversion steps taken, and another to add miscellaneous additional info about the title or author interviews.
Well, my point is, it made me realize just how powerful Calibre is and how much more it can do to make ebook reading and collecting enjoyable. It is one of the most versatile, feature-packed media management applications I've ever used and also currently one of my most valuable apps. And it's all free!
So I sent a small donation to Kovid today to show my appreciation. It wasn't nearly as generous as the one the OP made, as money is currently tight, but something is better than nothing. I'm sure if more people just donated a small amount here and there, it would add up and help ensure the continued development of Calibre. It's also a good way to say thanks.
So, thanks, Kovid, and long live Calibre!