There is a problem with the way Zotero handles case sensitivity of tags. If you have the same tag listed in multiple references but with different capitalization, for instance "Immersion" and "immersion", when you click either tag from the tag cloud, it will show all items which are tagged with either capitalization. This is great. However, there are two words in my tag cloud taking up space.

So I renamed all of my tagged references from lower case to upper case - they all now say "Immersion". The old "immersion" still shows up in the tag cloud. Thinking it was a distinct entry - since it shows up separately in the tag cloud, I right-clicked on it and selected Delete Tag. Unfortunately this not only deleted the lower case tag "immersion" it also deleted the upper case tag "Immersion" so now there are zero references with that tag, all of my work has been lost.

If Zotero is going to maintain distinct entries in the tag cloud, then deletion from the tag cloud should also be distinct to the case-sensitive values and should not delete both cases.