Editing is a good thing. What generally is the biggest taboo in editing is changing an answer/question so much that the OP's original intent is lost.
A lot of new users will post a questions that simply are good questions but written very poorly with little context. Or they often write a lot of context and forget to ask a direct question. Editing these types of posts to clarify the question, to add more context or clarify the context is not only fine but encouraged.
Answers the same way if you can improve an answer with an edit you should. The objective of the site is to have good questions and good answers, editing by experts helps that cause.
New people tend not to read the faqs, and other information and while they have a good question in mind they often do not write a good question for the site. It is the experts job to moderate these into good questions rather then close them.
You will note that once the site gets out of private Beta, into public Beta, users need more score to edit questions without peer review of those edits. I think it is 3000 points for a site and 1500 points for a site in beta to submit edits without peer review. This insures that the edits are made by experts or reviewed by the experts for a site. Which keeps the edits on topic and fair.
All edits can be undone. You may often find that an edit is bad, and choose to undo the edit or take a shot at the edit yourself. It is all about making a question or answer useful. All published writers are edited in book, articles etc. Writers hire people to proofread their work and suggest changes that range from correcting typos to changing whole chapters. We all own whatever anybody posts here in the sense that we want it to be a quality piece of work and we should treat it that way.
We also should help the new people that will be coming along, to edit a question so that they learn the SE ways of doing things. Editing is a valuable tool that helps a site obtain a good quality. Editing rather then closing is a much better way to engage a new user with the site.
So edit away and don't be shy.