In some answers references and links point to wikipedia articles, which may or may not contain good references themselves. Is this deemed as acceptable references? Personally, I dont think they should be valid to support key points in an answer since the quality of wikipedia entries varies quite alot. They are not a replacement for direct references to original research or review articles. However, in some cases I think they are fine, e.g. for pointing to basic defintions or topics.
For me wikipedia is a great source for popular science type questions and can offer simple explanations, as well as definitions/explanations of keywords & terminology (like that). But I also think, wherever possible, we should be referencing real publications to encourage non-academics who have asked questions to read and engage themselves in peer-reviewed science (I say non-academics because academics already read papers and are aware of the resources out there).
More technical/high level questions will also likely require more academic references because a wikipedia page is not likely to exist/will be insufficient.
We don't have any hard citation requirements here, you can certainly post an answer without any references at all.
Though I would of course favor answers that reference the appropriate scientific literature. But Wikipedia is fine for general explanations.
The only case where a lack of references comes into play is if someone makes dubious assertions without backing them up. This is a case where downvoting and commenting on the post would be appropriate, but a bad answer is still not against the rules here.