It may have a 'slight' effect re:+ Google. The crawler bots like to see updates and increasing content length, a reduction in the length (comments) may appear to the bots that the page has been damaged or severely edited.
They are programs what do they know?
They look for specific information.
As long as that is retained,
it should be fine to reduce the comments.
Check out the hubs on SEO for the things to watch out for. Or watch the SEO tutorial by hubpages staff.