I'll take a look pefferie. We've noticed just this weekend that popup behavior on iPad Safari is also sort of inconsistent.

We use some of the same tools for text annotation and editing, which is why there is some of this unexpected behavior. If you're reading News in Chinese and want to add a word, highlighting it and providing the definition queues the materials for review and eventual incorporation in our dictionary, etc.

As mentioned in a comment above, we're trying to figure out how to incorporate more etymology in the system. I'm not sure if we want to encourage everyone to dive-down to the character level with every word. But I agree we should provide more support for breaking down words and intuiting why characters are the way they are. A data issues as well as a UI issue.