Having a onebox and typing characters duplicates oneboxes, and also their icon if they have one.
It happens for various domains, it’s not related to Wikipedia oneboxes.
Steps to repro:
Paste a link that generates a onebox
Type some text in the composer
It’s likely related to a recent commit, as it doesn’t happen on my test instance 3.1.0.beta5 (78d8bd7c81).