In light of the non-web_source discussion taking place, or perhaps more specifically, the relatively minor part I played in it, bad source has come up (following concerns raised by RaisingK) due to similar reasons. That being, the additions I had made to the wiki following discussion on the Discord server. So I thought it would be appropriate to get an actual discussion going, and see people's thoughts and opinions, given good intentions. The edit in question being below.
This tag is used to indicate when a source does not directly point to the true source of an image. This includes redirect links, and links to a completely different image, but not direct image links.
If the source of the original image is found, please use it to replace the given source link (either as an image link or, ideally, as a post link).
The concern raised specifically by RaisingK is how the addition of "direct image links" corresponds in cases such as post #3913337, where the artist removed that page from the original Pixiv post in a revision. In regards to Pixiv cases, direct image links generally refers to those that aren't normalized, so bad source would still apply to those, but regardless;
The change, as mentioned, was inspired following discussion in the server, specifically in regards to the use of bad source in relation to bad link (the discussion itself, done in tiredom on my end, revolving around the usage of either in the case of Discord direct image links). The two would, in most circumstances, be mutually exclusive, due to the former being more on sources not pointing towards the image's true source (ala the examples named in the wiki article) and the latter being more on sources which are direct image links when they could be the OG post (due to the post likely having further info, such as commentary and tags, unless circumstances prevent the linking of said OG post, in the case of old blogs), hence why normalized direct image links don't count.
That said, there are circumstances where the two tags do collide, such as in the case of the following posts; post #231133, post #240432 (Explicit) and post #255342 (Explicit); where the direct image link source was presumably used by the blog to show the newest image posted by the artist. Under one interpretation of both the current wiki and the proposed edit, direct image link sources such as source:*i.4cdn.org/ count due to now, postmortem, redirecting to a 404 page.
With all this in mind, I thought the change was sensible, and naively, while based on discussion, ultimately unilaterally made the change to the wiki, for which I'd like to apologize for, given how large the tag is. I do still think the change is a good idea though, especially as it would clarify the distinction between the two tags further.
Whilst I'm at it, however, I'd like to bring up the examples named for what the wiki considers "redirect links". The Twitter example named, "https://twitter.com/i/web/status/12345678", seems somewhat counter-intuitive now that Danbooru normalizes Twitter links to use that format instead, whilst the deviantArt example, "https://deviantart.com/deviation/644661149", might prove difficult, given how for some deviantArt direct image links, that's the only link that can be derived, especially for older URLs. Cases such as post #3491465 make more sense to be named, given that such source links don't automatically redirect one to the post in question (and even if it weren't a redirect link, it'd still be a bad source, so there's that).
So, with everything said, I hope a proper discussion can be made, and perhaps a collective touch-up of the wiki, no matter how big or small, can be decided upon!