So I caved in to peer pressure
Over the past few weeks I have been hit by the spammers, subsequently I have blocked over 200 IP addresses from even reaching the site—not the approach I really want to take. So instead I have done what other people have done, with suprisingly good results.
I have added another input to my comments field called comment_username which is hidden by the stylesheet. Whenever the form is submitted with a value in this field it rejects the comment. This works by spambots just populating every input they see based on keywords (i.e. username/name/userid/un/ expects a name of some sort, content/comment/thought/say/voice expecting the main body of the post, namely their spam. Of course this is assumed by me.), and then submitting the form.
Time will tell whether or not this approach will work. If not then I have a few ideas up my sleeve which I can test and put into practice.