> or it is blatantly obvious

It falls under this case.

First, we notice the comment isn't an actual question, as there is nothing to actually be answered. This is a clear indication that its usage is therefore that of rhetoric. This is likely why they didn't respond, as there was nothing informative you could say unless you are significantly updating the premise which is being mocked.

Second, the diction and pattern of the sentence matches a commonly user sarcastic pattern of "wait, you're saying x but y?!" and the only thing missing is a surprised pikachu gif. It even does this at an abstracted level as it emphasizes the arbitrariness of the entity requesting the information. The pattern is up there with "I have a modest proposal" and I am having difficulties in even coming up with a more prominent pattern. There are several prominent memes built off of this.

Third, it involves additional flare to indicate a mocking of the obviousness of the claim made by the article which is summed by the parent. The comment is quite pejorative, with a clear disdain for the lack of accountability of the credit agencies.

As far as sarcastic comments go, this is about as blatant as one can get. Even my sarcastic addendum ("Is sarcasm dead?") is less obvious than the comment. Similarly the sarcasm you are employing is far less obvious. But none necessitate vocal inflections. I think your detector is defunct and you may wish to take it in for repairs or an upgrade.

I also disagree with your interpretation of when sarcasm works and I would suggest a different strategy. Your strategy will have a high false positive rate and teach you to misidentify sarcasm rather than learn to identify it. If a comment appears reactionary and condescending without a abundantly clear question to answer, either assume sarcasm or bad faith. In the latter case, one should not engage as you're only encouraging hostility. Simply downvote and move on. If you are wrong, you have just downvoted a sarcastic comment (which may not be adding too much to the conversation, as is the case here), which also sends a signal to the user that they need to work on their sarcasm or save it for other forums. You can take a middle case and hedge by saying "I think this is sarcasm, but if not..." This also goes with a different strategy of not responding if you don't have much to contribute. If you don't have a clear question to answer then the only reasonable responses are to ignore or ask for clarification, least you just create more noise. Internet conversations are well known to degrade easily and quickly.

We also should mention satire, as it is often employed. Satire's foundation is that of an alternative interpretation. The simple metric here is "would a reasonable person state this?" If there is any doubt to this, I suggest reading this document which describes the definition of satire while also making heavy use of it[0].

I mention that my addendum employs sarcasm, through exaggeration, but there is some real question to it, as lately I have seen severe identification even with the use of "modest proposals." Language itself is compression and if one is to take a literal interpretation of everything then you will be unable to accurately communicate and are likely to frequently enrage and annoy others. Due to the compressive nature, you will always be required to "read between the lines" otherwise even this sentence would be uninterpretable.

[0] https://www.supremecourt.gov/DocketPDF/22/22-293/242292/2022...