>But, why are some categories not updated for over a year?
Do the math. 600,000 categories, about 1 million visible edits a year, NOT evenly distributed (because ... more sites get reviewed more efficiently if an editor works on "batches" of sites in a particular category.). So it is not at all uncommon for a category to go that long between updates. Bear in mind also that in many heavily targeted spam magnets, an editor may easily do dozens of site reviews with no visible change to the category (and no change in the category updated date.)
>Is it possible they're being updated "from above" and the date simply doesn't get changed?
No. The other way 'round DOES happen -- top-level Shopping is rarely changed, although SOME subcategory is changed daily. (This sometimes confuses people who are used to the Yahoo! way of marking a "category change" all the way up the tree. In the ODP, only the actual category changed is marked, and it's always market. Well, almost almost always, and the EXTREMELY rare exceptions are software glitches.)
>For a category that has been recently updated, one which you've submitted to, and your link was not added in during that editor's update, is that a "tacit" rejection?
Absolutely not. The update happens every time a single listing is changed. An editor may done as many edits (or as few) as fit into his plans and his available time for the day. An editor may have visited the category only to fix a high-priority quality problem (say, bad link or misspelled word); or may have been working on sites found via Google or some other source rather than submittals; or may even have added a site he found while REALLY working on some OTHER category (to which he immediately returned); or may not have had time to do all the sites he knew about in that one session.
Really. This is not just "occasionally a wrong assumption." It is almost always a wrong assumption.
>I realize there's going to be a plethora of yes, no, maybe so possible answers ... but if updated and site not added, is it "safe" to resubmit without penalty?
Don't do that. As I say, it would be basing your actions on an assumption that is nearly always wrong. And it can even hurt. Suppose, for instance, that you submit your site to Widgets/Blue. Normally, resubmittals to the same category don't hurt. But in THIS case the editor looks at your site (it may even show in your server logs, although it doesn't have to) and moves the site to Widgets/Green, because that's the way WE classify Cyan Widgets. You immediately resubmit to Widgets/Blue. A couple of weeks later, the editor sees the submittal, and moves it to Widgets/Green -- again. (Remember, he probably won't review it for a listing -- he may not be ABLE to edit Widgets/Green, or he may not like to edit there, or he may just be focusing on this category -- which is the normal mode of operation, because it's more efficient that way.)
After a few months, you've got a while pile of submittals in Widgets/Green, and one ticked-off Widgets/Green editor thinking about spam penalties.
You may think you aren't in this situation, because you're sure you got the category right -- but most submitters don't, and the odds are against you. In fact, if you're really confident you got the category right, it's a pretty good sign you're not understanding the problem at all. (I'm often not sure about specific sites outside my area of expertise. And even inside my area of expertise, I'm sometimes sure only because I defined the taxonomy...)
Again, this is something that is different from Yahoo! (which, I understand, just deletes sites that are missubmitted.) We move them to a better category. (Well, supposed to, and editors who don't get a friendly reminder when it's noticed. An editor NEVER has to review ANY site, but SHOULDN'T make it harder for some OTHER editor to review it.)