We know that Google and Bing don't use the Keywords meta content for ranking or indexing. Yahoo notes this (when I last checked) and will show a site if you use some made-up word there, but whether it is used to rank is not known to me.
I use this plugin and I do enter a couple of keywords there but I don't obsess over those words or waste time choosing them. I am not looking at the plugin settings right now but I think there is a setting to use the tag values as the meta keywords. Perhaps that has been enabled for you.
I think there is a setting to use the tag values as the meta keywords. Perhaps that has been enabled for you.
It apparently is set up to use tags as keywords. I can enter keywords but, as mentioned, I was told not to.
So then, it's okay that keywords are often quite removed/vague from the actual subject of an article. For example, an article might be about Barlow microscope lenses but the keyword in the source code is accessories?!
I've never used All-in-One SEO Pack on my blog. Most of what I want to do is part of my theme (Thesis) out of the box. I can control things like the <title>, meta description, and meta keywords of every post on my site and static page on my site.
I'm not sure why anyone would have told you NOT to enter keywords for each of your pages unless it's buggy for some reason. While keywords are NOT considered in the ranking algorithms at most engines, Danny Sullivan proved a month or so ago after Yahoo! announced at SMX that they did NOT use keywords that Yahoo! DOES in fact still use them in their algo.
I still always include 5-10 keywords for "completeness"... not for ranking purposes. The element has been around so long, it just doesn't seem right to have an HTML/XHTML document without them. LOL
I would try entering them using All-in-One SEO Pack for one of your pages and see what the resulting HTML looks like. As long as it generates a valid HTML/XHTML document with a single meta keywords element and includes your targeted keywords that you enter, I'd use it unless someone can give you a really good reason not to do so.
I would rather have NO meta keywords element than to have a meta keywords element that contains keywords NOT relevant to the page. I typically only include words/phrases that actually appear on my page... and only a handful.