Labels disappear when renaming!
Currently if one label is renamed to match a second label then one of the labels will disappear. This is clearly not optimal/predictable functionality.
Instead make it so that when a label is renamed to an existing label then they are merged!
If you are wanting to merge to labels, you can instead just remove one of them and accomplish the same result. Though feel free to add this to our votebox: http://todoist.com/Vote/
How can I do that? I want to merge two labels spanning many non-overlapping tasks, not relabel each task one at a time.
ANYWAY the behavior is clearly not right. Renaming one label to match another should at least produce an error, right now it just results in the erratic behavior that one of them disappears.
It's indeed not possible to have two identical labels in our system, we'll look into creating an error message upon an attempt to reuse an existing label name.
For now, the only way to tag a group of tasks with an existing label is to edit each task one-by-one. Sorry for the inconvenience.