Many answers on Mi Yodeya include sources, often from rabbinic literature. Many times the entire answer can be a quotation from such a source.
I would think that the simplest and best way to pose a source-based answer is to simply say "Source A says XYZ". A can be a Talmudic passage and XYZ can be the content of the passage either translated or summarized. However, I often see posts where a source is used to answer the question, but the source is not cited directly. For instance, an answer might say "according to this Wikipedia article the Talmud says XYZ" or "So-and-So wrote an article about this citing the Talmud which says XYZ".
To me it seems that such answers have lower value. Why cite a secondary source when a primary source is available? When citing a secondary source, one is relying on the authority of the secondary source (which might not be very authoritative) instead of relying on the authority of the primary source. (In fact, if I am reading something and it cites a secondary source instead of the primary source it sometimes raises suspicion of obfuscation.)
(I understand that sometimes an answerer can find a secondary source but lacks the background to engage with the primary source, or the secondary source does not give enough information to locate the primary source. However, I think that one can usually find the primary source with some degree of effort, and if the primary source cannot be found or understood then the secondary source should not be used as an answer.)
I think that an obvious exception is where the answerer is citing a secondary source to bolster the authority of the primary source. For example, if I can just cite a Talmudic passage, or I can cite a rishon citing the Talmudic passage, the latter presumably has more value because it shows that the rishon ruled according to the Talmudic passage in practice. Similarly, if I can cite a rishon or I can cite a later responsum citing the rishon, the latter has more value because it shows that the posek ruled according to the rishon in practice.
(Even within this exception, I would think that it would still be better to cite the primary source in addition to the secondary source.)
But barring this exception, is there any value to citing secondary sources? If not, how should one treat answers that cite secondary sources? (E.g. edit, downvote, comment, etc.)
(It is possible that someone would cite a secondary source because that is what led them to find the particular primary source, but I don't think that is a necessary level of attribution.)
An example of the type of answer I am referring to is this (nothing against the particular user).