Yesterday I observed (on my cellphone) that Google returned a top-level "snippet" for
graph isomorphism that quoted this old (and incorrect) Answer.
Normally I do not feel obligated to delete an Answer merely because it is wrong, but in this case the error was being highlighted by Google and its author had not been back on the site for about the length of time since it was posted.
Google does have a mechanism to give feedback on the highlighted search results, so I took the opportunity to suggest their search results ought to take negative vs. positive votes into account (it appears in the desktop results that they do).
I'm suggesting that this particular wrong Answer could be deleted, to avoid giving Math.SE and StackExchange more generally a poor reputation. A consideration is the length of time in which the an author has failed to at least acknowledge the error.