Is
<meta name="keywords" content="mykeyword, Mykeyword">
the same thing as
<meta name="keywords" content="mykeyword">
Are both keywords considered the same by a web crawler?
They're not case sensitive, but they are useless from an SEO point http://www.mattcutts.com/blog/keywords-meta-tag-in-web-search/
If you search for "People" and "people", you'd get the same results. Word case isn't important in title tags, header tags, or any other tags, so they shouldn't matter in meta tag, either. So for all practical purposes, "people" and "People" is the same word for the crawler.