Good questions!
How much of an edit should be allowed when it seems the proposed
editor is ripping the personality out of a post, or adding correct
punctuation and grammar?
From the help center:
Edits are expected to be substantial and to leave the post better than you found it. Common reasons for edits include:
- To fix grammar and spelling mistakes
- To clarify the meaning of the
post (without changing that meaning)
- To include additional information
only found in comments, so all of the information relevant to the post
is contained in one place
- To correct minor mistakes or add updates as
the post ages
- To add related resources or hyperlinks
In the case of the first suggested edit you mentioned, the post is improved by the addition of code formatting. This helps other users by making the post easier to read. And it helps the original poster in two ways 1) it teaches them to add code formatting and 2) it increases the chances of them getting a good answer (because the post is easier to read).
Spelling or grammar corrections that make a post easier to read are substantive enough to be warranted, in my opinion. And if while they're making a substantive improvement (like adding code formatting), I think it's fine to do some really minor grammar or spelling corrections, as long as the spirit of the original post is unaltered.
For the second suggested edit you linked to I think the edits improve the readability of the post without changing the spirit of the post, so I agree that it's helpful.
What's wrong with personality and politeness in a question?
Nothing, in my opinion. I don't think editing a post for the sole purpose of removing a "thank you" at the end qualifies as a good edit, since it doesn't substantially improve the post. I don't feel it's necessary to remove a "thank you," but there are differences of opinion on that!
How does a new user feel when their grammar and tone is corrected on their
question?
I think if the post is edited carefully, so that the changes don't alter the original spirit or tone, it should be OK. But I think you're right it should be treated gingerly.