If you want, you could use GMail filters to delete those emails automatically. Here’s how:

1. click the engine button (settings), then “see all settings”, then “filters and blocked addresses”.
2. click “create a new filter”. Add “top of Google search” to the field “has the words”, leave other fields blank.
3. click “create filter”, then check the “delete it” box, then “create filter” again.
4. repeat steps 2-3 for other shit that SEO spam is likely to mention.

Important: never use as a filter anything that legitimate users might reasonably say. Only things that you’re fairly certain to come from a spammer.

EDIT: I repeated two steps without noticing it. My bad.