Personally, I think tipping rather than (or in addition to) upvoting might be a better way to counter "erroneous" downvoting.

The reason for that is, when you upvote a downvoted post, you are throwing away a sizable portion of your curation rewards (50% if you exactly counter the amount of the DV). For the curation rewards you are going to be throwing away, why not just tip the author directly instead (or even tip a bit more, to signal to the DV'er that every time they DV, they will actually be indirectly adding to the perceived 'over-reward')?

There are really two issues at play when it comes to countering an erroneous DV:

1. Restoring author rewards to the author who was downvoted.
2. Restoring curation rewards to the prior upvoters (i.e. those who upvoted in good faith, because they genuinely valued what the author had to say).

Upvoting the post the full amount of the DV does both, but only partially when it comes to #2 (50%). However, it cuts your own curation rewards in half. So, it might be best to [1] tip the author half the amount of the lost author rewards (which would equal your would-be lost curation rewards) while [2] compiling a list of the curators who had their curation rewards zeroed, then [3] go out of your way to upvote future posts by the original author and the curators more so than you otherwise would have, in order to bring everyone back to wholeness (or, as mentioned above beyond wholeness, to make the DV'er complicit in supporting that which he/she is trying to subvert).