Having read the spear wiki, I'm not convinced that it is optimally defined. The wiki says "sharp, pointed blade", implying that non-bladed weapons aren't eligible, but such a definition excludes javelins, which I would consider thrown spears. (Plus I really think the Lance of Longinus is a spear from a common sense point of view.)
Spear the Gungnir is, I suppose, a matter of opinion; I would call all three of the posts you linked in the other thread "clearly spear-shaped" (well, maybe not the third one, but that's more an issue of sketchy art than it is one of conscious design decision). On the other hand, closer inspection reveals that Laevatein is often represented as a bendy mess as per ZUN's original art, so an implication to spear or polearm is probably a bad idea in retrospect.
So, take two:
Mostly it would just bug me if named weapons weren't findable under a search for some general tag. At the very least, I think we can all agree that all of the above can be implicated to weapon if the above implications don't meet with popular approval.