I vote where I recognize and appreciate value.
Partly, to keep the energy in flow proportionately.
Partly, to set an example for onlookers so others may see and learn what value sticks out and is worthy of reward.
Your comment is one of the best here - thus, in my opinion, well-deserving of being bumped to the top with a reasonable dollar figure attached, so as to provide a fine example of how comments are done excellently. ;-)