The utility of the similar account message could be improved significantly by linking to Special:CentralAuth for the conflicting user accounts. I believe this would be more useful than linking to Special:Contributions (proposed in T42576), especially when the conflicting account may not exist on the local wiki.
As you know, Special:CentralAuth provides a full overview of the global user activity, what wikis they're active in (if any), account creation date, and home wiki - all the information that allows account creators to make a quick determination of whether or not the account qualifies as "dormant" under our similar account policy (which feeds the decision on whether or not to ignore the AntiSpoof check). Providing these links in the AntiSpoof results would make the ACC workflow a bit more streamlined by removing the need to manually lookup the similar users.
I would just implement this via userscript, but it seems they are not active on Special:CreateAccount (and for good reasons too).