So far the people getting these bursts of votes are pretty prolific posters. It's possible that somebody, perhaps a newcomer who doesn't know all the ins and outs of SE, sees a good post, says "hey that was good; what else has that guy written?", clicks through, and starts reading and voting. Then, usually, it gets reversed the next day, so the person who felt great yesterday gets a big disappointment today.
I understand the good intentions, but this is not the best way to use the site. It's better to just use the site normally, voting as you go. I hope whoever is doing it sees this discussion.
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It's great that you're enjoying the site and rewarding good posts; we want you to do that. The tools, however, can't always tell the difference between that and "I'm gonna go vote for my friend" and the latter's not ok, so sometimes well-intended votes get reversed because they look like the other sort.