If the user name isn't suffixed with the diamond (♦), it is definitely an ordinary account. ¹ By the way, StackExchange does have a "special" bot account Community♦.

As of now, there are no special "vote to close" accounts I know of, but even if StackExchange introduces one in future, you can be sure it will have the ♦in the user name, it will make its purpose amply clear in the profile, and most importantly, it won't post an "answer" to close.

If you come across more such trollfascinating accounts ("vote to delete", "downvote this answer", "ban this moderator", etc.), just look for the diamond.

¹ The most common use of the diamond, of course, is to indicate that the user is a moderator. However, StackExchange employees and "special" accounts also have it for exactly this reason, which is to avoid users from misleading others or misrepresenting the site.

As of now, there are no special "vote to close" accounts, but even if StackExchange introduces one in future, you can be sure the user name will be suffixed with the diamond (♦) character. Moreover, its purpose will be clearly described on the profile.

Ordinary accounts are not allowed to use the ♦ character in the user name to prevent users from misleading others or misrepresenting the site. It is attached only to moderator accounts, SE employee accounts and the special SE-administered bot account Community ♦.

If you come across more such troll fascinating accounts ("vote to delete", "downvote this answer", "ban this moderator", etc.), just note the missing diamond. Such user accounts are invariably created for "interesting" activity, which you should also downvote and flag to moderators.