It seems really supportive to get a comment from a supposed reader of your genealogy blog that compliments you on your writing ability or on the wonderful content. The problem is that the comments are bogus. They are really links to a business or worse and generated automatically by spammers. They are really easy to spot, if you review all of your comments before you publish them.
The hallmark of the spam comment is a mention of an entirely unrelated business or organization as part of the comment. I preview all of my comments before publishing them and recently have seen the incidence of spam comments go from one or two a week to one or more a day. At a minimum you should review and approve any comments before posting them online. Here is a link to Google's explanation about moderating comments.