If an answer gets deleted by a moderator - presumably because it was considered a duplicate - why would said moderator delete the first answer in the timeline, especially after the poster has put in time to clarify the question? Should s/he not delete the second answer, which copies the first?
Sometimes posts are duplicated and a screenshot added to make it appear as if the duplicate answer brings something new to the thread (which it really doesn’t). This not only lowers the quality and usability of this site, but also leads to a points collecting mentality in which adding screenshots to text answers becomes common practice - not to talk about wasted space and fostering illiteracy.
Its deletion also antagonises the poster of the initial answer (who spent time ascertaining the correct one, improving the question and subsequently formulating an answer), which s/he then might feel is a waste of his/her time and eventually stop frequenting the site. This in turn leads to an ever increasing amount of unanswered questions.
At the very, very least and if it is commonly agreed upon that screenshots are necessary for less literate people to understand the post, adding it to the first and correct answer should be sufficient, which can be easily done via the “Edit” option. The same goes for formatting.