They're just posting to get the link to their website in the signature. It's a good idea to have a link to your site in your signature (where allowed by forum rules), but to make a post ONLY for the purpose of getting a link to your site - that is poor form and can get you banned from many forums.
Quick little SEO lesson
They did attempt to get relevant keywords to help their site rank well for the phrase "carpet upholstery cleaning services" - but this is too broad. They will be competing with EVERY carpet and upholstery site worldwide for the same phrase. Are they going to service the whole world? Of course not.
They (and you) will do better to add in a geographic qualifier so that you are more relevant to your local customers who are searching for your services.
Carpet Cleaning in Baltimore, MD
Carpet and Upholstery Cleaning in Baltimore County, MD
• Add some variety of phrases.
• Be sure to check the forum for the "nofollow" tag - links there will do nothing for your SEO
efforts. (this forum does not use the "nofollow" tag)
• Contribute to the value of the forum - don't just post for links.
• Use good "link text" instead of just posting www.mycleaningwebsite.com
in your signature. The link is basically a vote tallied by Google that your site is a good resource for "carpet cleaning in topeka", instead of just the website URL. Getting lots of linkbacks (votes), combined with supporting text on your site can get you moving up in page ranks.