I may be misinterpreting them but from the "wallet codes are ok" part it sounded like they weren't banning them.
If by shadow ban they mean the link is completely inaccessible to other users then I'll agree that they were doing their part and banning links to their site was excessive.
"Due to the nature of JSFiddle, anyone can post anything", therefore "wallet codes are ok" since "anyone can post anything".
A shadow ban normally means that you, the creator, can see your content, but nobody else can. So them shadow banning people who post wallet codes is the direct opposite of allowing wallet codes.
> we did implemented a content filter to shadow-ban these
JSFiddle shadow-ban these scam accounts, and they asked Twitter to do the same but Twitter bans _all_ JSFiddle URLs instead.