was it by any chance an @ memtn you pasted in?

I did not paste it. I manually typed @ + three letters and then clicked on the article I wanted.

This has happened on multiple articles. And the display always leaves "@abc", but never completes the article mention.

that means that the process was not saved - try after pushing enter to give it one ore space character - this should solve your issue for now. This editor is being redesigned so you will have a much better version soon :)