Andrew Gray wrote:
A lot of problems - certainly back when I was still regularly dealing with OTRS earlier in the year - came from patrollers assuming that an imperfect or confusing contribution was vandalism, was spam, was malicious. They acted accordingly - reverted or deleted and warned - which just confused and upset the subject.
"If it isn't clearly vandalism, don't treat it as vandalism" might be an interesting approach.
In my own patrolling (admittedly infrequent these days since I find writing new articles less annoying), I've gone back to my circa-2003 way of dealing with the problem, before user-warning templates existed: just post a short note on the user's talk page telling them that you undid their edit and why.
For example, if someone removes an entire section with no edit comment, I'll write something like, "Please don't remove sections of articles without discussing on the talk page or at least providing a reason in the edit summary. I've added it back for now. Thanks!". (Credit goes to Brianna Laugher at Wikimania '07 for suggesting that approach.)
I do find a pretty large percentage of things that aren't *obvious* vandalism are good-faith errors, and some of the people who made them even respond with apologies after being "warned". Some amount of judgment is needed of course---if the edit is from an IP address that's been tagged as belong to a library or school computer, I usually don't bother to spend time doing that.
A totally different and somewhat circular problem I've noticed lately is newbies biting other newbies (or even non-newbie editors) by taking on new-pages patrolling duties before they really know what's going on. That requires basically a nice way of saying, "look, you should really stick around a bit more before you start going on new-page patrol and tagging articles with cleanup/delete/unreferenced/etc. tags". Heck, I had one of my articles tagged as "unreferenced" by a new-ish editor because it "only" referenced a book---as he explained, it didn't count as verifiable if there were no links he could click on to verify it. =]
-Mark