I am talking about stuff like principle/principal, its/it's, your/you're, effect/affect.
Can I correct these things even though the meaning of the question/answer is clear?
Would it come across as rude, or as an "overkill"?
Even if it is by a small amount, corrections like these still improve the clarity of the post. However, I would encourage you to follow the advice of the help page, and look to see if there are any other problems you can correct while you are editing.
Yes, please do. Such changes make the site easier to use for all readers.