<p>I think you'd be well advised to look through discussions on SE Meta. I have bumped into numerous discussions which raise the issues you raise and others linked; I have never searched for more. </p>

<p>But the bottom lines appear to be three-fold: </p>

<ol>
<li><p>Some changes in reputation are automated, driven by automated attempts to spot unacceptable behaviour. </p></li>
<li><p>If someone is downvoting in a nasty way, then among those there are mechanisms to spot that and if need be discipline or remove that person, in which case your reputation should be corrected in due course </p></li>
<li><p>A great deal of thought has gone into how to handle this and it is only "reputation", not reputation (win some, lose some). </p></li>
</ol>

<p>So multiple downvoting, as it appears to you, is <strong>not necessarily evidence of individual nastiness or spite</strong>. So the obvious conclusion isn't quite so obvious.</p>

<p>EDITS (1) in reaction to helpful comments may make some comments below seem mysterious. </p>

<p>EDITS (2) in reaction to @whuber's reply, which is naturally definitive. </p>
