This is just my opinion, not any kind of official statement.
There are a number of factors that go into a good post. Some of these are delineated at https://judaism.stackexchange.com/help/how-to-ask and https://judaism.stackexchange.com/help/on-topic and https://judaism.stackexchange.com/help/how-to-answer. Some others, here on Meta, are linked to from Isaac Moses's answer here.
Among those factors is clarity. A typical reader of a post should understand the post; for an answer, the asker should. Ideally, even an atypical reader should. There's more detail on this on a number of the help pages and Meta posts, above.
Sometimes adding stuff to a post improves clarity. Sometimes it reduces clarity. Sometimes, one needs to remove some stuff and add other stuff in order to achieve maximal clarity. And then, sometimes, adding stuff reduces clarity but should be done anyway in order to make the post rate higher on one of the other quality measures I allude to above.
(I imagine it's extremely rare that adding something to a post will neither improve nor reduce the post's quality.)