It's your blog. Edit it how you like.

However...

Realize that bots are taking snapshots, and people are referring their friends. So if what they're interested in isn't here when they arrive, or has drastically changed, they probably won't ever come back might get confused. And remember, the key is more readers over time, not less.

I'm not talking about spelling or grammar corrections here, but substantive edits that change the meaning or expand upon the original copy.

Two techniques that I've come across that work when you just need to edit but still want the original text to be seen:

• An "UPDATE:" entry at the bottom. This is good for when there's new developments, or if a comment has caused you to reevaluate your position. Or if you've just found some new stuff to share.
• Strikout is the absolute best a really great way to indicated small but important changes, while still preserving the original copy.

UPDATE: A 3rd option is to use the editor's builtin "Reason for editing", but I personally feel this is weak and likely to be overlooked. Did you see mine up above? Plus each reason overwrites the previous one.