I was never really encouraged to fill in comments, it always just seemed like somewhere my instructor signed and filled in but looking back now I wish I had put details in of those early flights.
I would never have dreamed of signing across the page. My logbook used to be immaculate, and my instructor used to say I had the neatest logbook he haad ever seen. I used the same pen, block capitals, as neat as I possibly could etc and then when when I passed my GFT - WHAM - the CFI goes and stamps a great big red stamp across the page!
But anyway, to answer your questions and stop me rabbiting on... My logbook has a little part at the bottom right of each page to sign and I always wright SELF - its shorter then my surname!
CBK