The Problem (an example)
This user's answers have been downvoted consistently as they are not very high quality.
The also tend to come in bursts of nearly 10 often on older questions.
They are not low quality enough to trip an automatic ban, apparently, but as you can tell many of the answers are downvoted and only a few are actually positive score.
Unfortunately this problem has been made worse because of the following:
I understand the importance of having a mechanism to prevent users from simply going to a user and downvoting all their content, but it causes situations like this to be really difficult.
Resolution
I suggest the serial downvoting algorithm only consider content with a non-negative vote count. Perhaps even make it so all content with score of < -2 and posted within the past 24 hours.
Or, preferably, simply make it only apply to users with a median score of at least 0 OR less than 10 total posts (this would mean the algorithm would apply to nearly everyone except people consistently posting low content).
A user spamming nearly 10 low quality answers in a single day should not trip the serial downvoting algorithm, ever.
This comment is worth including:
it is worth noting that, as opposed to SO / active tags, at smaller sites cases like that would be more accurate to qualify as content-targeted (ie legitimate, as opposed to abusive user-targeted, intended to be dealt with by vote reversal script). When crap-bomber unloads their answers, those looking at slowly changing active tab at front page of the smaller sites are literally forced to see the new content to vote on - it's not like when one picks a user profile and bulldozes over their posts