4serendipity - 6:14 pm on Jan 30, 2012 (gmt 0)
I am wondering, though, if a site is using a tag in the wrong way, could this work against a page/site and affect rankings?
I doubt that element misuse would mess with rankings too much. I've noticed little difference, if any, between <b> and <strong> from an SEO perspective. The correct use of semantic elements should be taken seriously if you take pride in your work and want to provide the best user experience to everyone, but for SEO it doesn't matter much.
While much HTML misuse doesn't seem to matter, it's probably still a good idea to avoid outright spammy-looking things. Wrapping all of your paragraphs in something like <strong style="font-weight:normal">... </strong>, in addition to being ineffective for SEO, might be tempting fate a little too much.