The poster said "getting rid of 'made with xara' isn't an answer to the problem". No, it isn't, but if your main objection to having it in the head is that of outsiders snooping on your design method for whatever reason, removing it will help, either in the short term or the long term. Whether you are correct in your assumption that that's why you lose out on the SEO work is another kettle of fish, but removing all possible objections first may help you identify the real objection.

My quotes are not random. But maybe the thought processes that encourage them are...