This edit is actually not an error - we default to casts because sometimes characters are played by multiple actors at different times. That's why it requires the brackets. Your new version is equally correct, since only Sean has played Carter. Nothing wrong with what you did, just an unnecessary change. It doesn't harm anything either way.
It might be a bug in the coding of the infobox, or maybe the wrong infobox was used. But I know there is one that functions like this. I did go back and notice it was missing, however I also saw that the coding appears to be correct, hence my thought process.
Wow, I had no idea I even did that. I don't think I would have done it on purpose, because I don't mess with translations from Japanese. The only reason I would have touched that page would have been to correct a double redirect, but it doesn't look like it was a redirect in the first place. I guess I did something weird on accident when I was fixing a lot of double redirects all in a row.
I apologize for the inconvenience, and I'll watch out for that in the future.
A group of users came here to try to disrupt our community, hell-bent on not following our rules. When they made a post on my wall using foul language and baseless remarks, and having no other edits, I had no choice to block them. They didn't like that, so they declared war on us, getting all of them blocked permanently and Wikia Staff stepped in and told them to go on their way. They will not be unblocked under any circumstances, and anyone else who opts to come here to start trouble will find themselves met with similar punishment.
It's not a problem. I am a regular, but I'm not online all the time and I don't know everything that happens. Sometimes I see what people post on other people's walls because it shows up in the Wiki Activity feed.