> The original sentence was a little confusing:  "To get a list names
> ever exited in monthly worksheet."
> 
> I changed it to: "To get a list of all names ever exited in each
> monthly worksheet."

You failed to identify that **exited** isn't the correct word grammatically.  The author was looking to use **existed**.  Even the correct word, that the author meant to use, is a poor word to use which means a different word should have been suggested (i.e the word *created* or *generated*).  You failed to correct all grammatical mistakes in the answer.

> I think it's much easier to read if it uses correct grammar, especially because I made sure not to change the original **intent**.

I don't agree with your conclusion.  You failed to address even half of the grammatical mistakes in the answer.

> Again, you may need formula like `if(isna(vlookup(...)), "",
> vlookup(...)` to get rid of the `#N/A` text when a given name not
> found for some specific months.

Should have been:

> Again, you may need **a** formula like `if(isna(vlookup(...)), "",
> vlookup(...)` to get rid of the `#N/A` text when a given name not
> found for some specific months.

You failed to identify the grammatical mistake in this sentence.

> Once the *full name list* is got, later monthly update can be
> appending name list from new monthly to *old full name list* then
> re-filter it.

Should have been:

> Once the *full name list* is **determined**, **future** monthly update**s** can be
> **append the name list from the previous month's list and then re-filter it.**

> From a database's point of view, this is in fact to get a union of
> name lists in monthly worksheet (including removing the duplicates);

Should have been:

> From a database's point of view, this is in fact to get a union of
> name lists in **the** monthly worksheet (including removing the duplicates);

I would like to add, even my suggested corrections to the author's extremely poor answer, does not address all the issues it has.  Most of the original sentences don't actually make sense.  The quality of that particular answer is extremely poor.