A few weeks ago a collegue of mine discovered a strange behaviour in Sitecore’s package tool.
We needed to deploy some template updates to a client’s preproduction environment. We had some items that we did not want to be updated in preproduction. Instead of having to include each item or make some more or less successful query he decided to exclude the item (Like so)
The result was not quite what one would expect. Instead of leaving the item in preproduction the whole section was deleted causing a lot of weird error all over the application.