A user recently reacted with frustration when a post of his was closed, so I added a number of advice comments. When I interact with a user in this way, I sometimes poke around their account to sample some other questions.
In this case, many of the previous questions are too broad, don't feature code, or have been abandoned without responses to seemingly helpful answers (the last one is a great personal annoyance, and I often downvote it in the hope it will change behaviour). I would be inclined to downvote quite a lot here, but there must be a point where downvotes focus too strongly on one user.
I seem to recall that 20 up or downvotes triggers the reversal script, but I'm interested in the spirit of the law here. If 20/day is the limit, is 10 downvotes for one user acceptable? Since I am judging all posts on their individual merits, it's not voting fraud or mean-spirited downvoting, but I accept the automatic system (and moderators) won't be able to tell the difference.