It is difficult to say what "should" or "should not" be an artifact because it is—by definition—subjective. However, users tend to have a "feeling" about what constitutes an artifact and what doesn't. These feelings tend toward lore significance and uniqueness. When I say that the Targe of the Blooded should not be an artifact, I am saying that it has no historical value whatsoever, and is simply a unique looking shield with a unique enchantment on an item that appears once. That doesn't ''feel'' like an artifact to me, or to many others based on the discussions had over this topic in the past. This is a subjective consideration, but one that should absolutely be kept in mind when considering that our current definition is insufficient.
*2. '''There are many items which do not fit this definition and yet are still considered an artifact by exclusion (ie. [[Skyrim:
Dragonbane]], [[Skyrim:The Rueful Axe]], [[Skyrim:Morokei]]).'''
Like above, players and wiki editors ''feel'' like certain items belong in the list of artifacts, such as
Dragonbane or the Rueful Axe, and yet they simply don't meet the requirements. Dragonbane isn't the only weapon with its model, for example, meanwhile Morokei and the Rueful Axe have generic enchantments. However, wiki editors and players have made exceptions to the rules and listed all of these on the Skyrim namespace's Artifacts page. We could simply remove them, sure, and enforce the rules with an iron fist, but consider for a moment '''why''' people added those items to the page. They added the items because they believe that the item is an artifact, and that our current definition is insufficient.
*3. '''It is inconsistent with the definition used by the [[Lore:Artifacts]] page'''
** ...well-known among the people of Tamriel.
** ...associated with a Daedric Prince, Aedric God, or other deity.
** ...described in the in-game literature of Tamriel as an artifact.
This makes no claims about the uniqueness or quality of its enchantment, the uniqueness or quality of its appearance, and indeed even the number of times it can be acquired in a game (though an item can hardly be considered historically significant if it can be replicated so easily). However, this definition enables us to include items that are otherwise excluded but shouldn't be and also exclude items that are currently included but really aren't artifacts. While these rules allow for some measure of subjectivity, they also provide measuring sticks that we can use for determining just how much of an artifact something is. For instance, the Rueful Axe is associated with Clavicus Vile, and therefore absolutely is an artifact. Meanwhile, Morokei is a historically significant artifact of the first war with the dragons. There might be some opposition to this definition because it includes some measure of flexibility, but I firmly believe that ultimately we as a community can come together to discuss something if it is ambiguous, and that we should pursue the best definition of artifact even if it requires we discuss any possible borderline cases that come up over the course of current and future games in the series.