"Tiny, trivial edits are discouraged" but it's always helpful "to make the post significantly better when you edit"
In the particular example you've cited, it seems clear to me that all the changes were improvements to comprehending the problem:
- Typos are errors. Fixing the typo fixed the legibility.
- Mixing contractions and possessives with 's makes parsing visually difficult. Using the 's only where necessary (the possessive) simplifies parsing.
- Parenthesizing the majority of a post's content violates the purpose of parenthetical expressions and confuses the intent of the content. Removing them avoids making the entire post look like an aside.
I know your question isn't about this particular example, per se, but examine that example and my bullet points above in light of site policy:
Tiny, trivial edits are discouraged - try to make the post significantly better when you edit, correcting all problems that you observe.
If an edit makes the post significantly better by correcting observed problems, it is by definition not a tiny, trivial edit. The number of symbols changed isn't what's significant; whether the post is better after the change is the deciding factor.
So let's consider a hypothetical example where an edit occurred to the same example post, but instead of the three changes above, the following three changes were made:
- Putting a comma after "If someone dies."
- Changing "easy to consider" to "straightforward to treat."
- Removing the quotation marks around the "physical person" and "meta-person object" phrases.
Then the total amount of content changed is actually more than what was changed in the real example case, yet the meaning wouldn't be more clear to a reader than it was before, so it wouldn't have been a significant improvement. That's what a tiny, trivial edit would look like, and site policy on those is pretty clear.
TL;DR: So, how trivial is too trivial? By definition, if it's a significant improvement, it's not trivial and should be encouraged. If it's not a significant improvement, it's trivial and should be discouraged (or rolled back as necessary).