Grammar Check

The third one looks good to me, but what do I know?

Funny, the third one looks good to me.

Do either of you have a reasoning to why you believc that is grammatically correct?

Yes

It's the possessive apostrophe. Users, because there's more than one of them, ends in s. When attributing a possessive apostrophe to a word that ends in s you can just add an apostrophe or apostrophe s. So Users' or Users's would be correct, but most people drop the extra s so they don't sound like Hissing Sid.

Block users' signatures.

Nope. A plural noun like users which already ends in s takes only a following apostrophe:

the girls' excitement
my parents' wedding
both players' injuries
the Klingons' attack
the ladies' room
two weeks' work

http://www.sussex.ac.uk/informatics/punctuation/apostrophe/possessives

Here's a tricky one - In two weeks time (Ungrammaticised)

When it is one measure of time, the apostrophe goes before the s: one day's pay, one week's time. When it is more than one measure of time, it goes after the s: two days' pay, two weeks' time.

Is that specific to values of time or values in general?
I'd have written 'One weeks', Two weeks' out of habit.
I write as I choose, but refinement costs, but the will to do so.

I would say that all values or properties that are written using possessives have the apostrophe before the s for one and after the s for more than one.

One elephant's weight, two elephants' weight, one lamp's light, two lamps' light, one dog's tail, two dogs' tails.

Looks good to me!

Cory we might need a bit more context. In #1 for instance if "Block" is a verb and if "Users Signatures" is eg the name of an org then #1 is okay. Otherwise:

#2 is okay if a single user provides multi sigs

#3 if more than one user is involved


There's are of course any number of alternative terpts. For instance Block Users might be a fella's name, whereupon only #3 qualifies


Fellas let's thinka sumoraven