Editing answers to improve them is a generally good idea, but sometimes people don't like it when posts are edited away from the OP's intent. There is a wide gray area in the middle that's a bit hard to navigate.
But should you find yourself uncertain, it is always find to post a better, complete answer. Further, one should think of comments as being fundamentally temporary --- sometimes they get deleted and no one really thinks twice. When asking yourself "Hmm, should I collect a complete answer from a collection of comments", the general answer is yes, go for it.
There are also semantic reasons for making a complete answer, especially as opposed to a series of comments. People vote and edit posts, not comments --- so small typos in comments are more challenging to note and correct (especially within long comment threads).
Retrieving posts through the StackExchange API makes piecing together comments into a single very annoying. Similarly, having piecemeal answers affects search engines when they crawl the site --- but having a single complete answer makes it more search-visible.
And still further, navigating comments happens to be much more annoying through accessibility software (such as screen readers), to the extent where I've seen many people using accessibility software simply ignore comments altogether.