For the buyer:
Receipt, yes.
Vouch, not required.
To place more context to avoid you being confused, i'll explain a bit further with your thread for example -
BIG ORDER
NMZ READY accounts
What's your best price? 
if i'm not mistaken last time you posted this you wanted it for 25M or something which adds to around $8-9 on average per account
If you was new to the server and this said person who completed the service was looking to trade you and was like here bro heres my vouches look at them, then new users wont really know much different. They will think because let's say this person did again with the random number being x10 of these accounts for you let's say spaced out between different lengths of time to gain more vouches that this person is "in fact trusted" because of the number count and not the quality
However, if it was listed that let's say the person did $8 worth of work for you, was a solid person to deal with but in fact it was "only" $8 would then guide them back to questioning if and why the person should be trusted and if let's say a middleman should be used
1-36 WC takes 1 hour
Multipled by 10 accounts
Vouch would be 10 hours of free work completed.
Correct, it does literally take ~1 hour but at the same time it doesn't mean that the person is going to go out of their way to do hourly free work over a overall job vouch, which is the issue between the two and exactly what I am trying to pick at which you seem to not understand
It's a lot more useful if total hours are stated (Just an idea).
I strongly disagree with vouching buyers though (ignoring workers).
And again, unless the person was let's say a hourly charge like they do 1 hours free work then this wouldn't really do much. With that being said though, the person who is the one requesting would realistically have to list that the person did 1 hours free work and then it would be down to the person themselves afterwards to read the persons vouches specifically and see what they have done
On another website I recently came back to, I have 52 feedback, most of which adds to around 30-50B in gold sales, this means I am in fact more trusted than most people with the same amount of feedback than me but people will still prefer them over me even if they have a higher feedback but less quality
As for the worker part, yes workers should never be vouched for on Sythe. I mean if you're saying it as like "2easys worker <name> was so good man, proper good work 10/10" on
YOUR thread yes that's fine though as it's the same with gold sites. It is still your name, still your business not the workers and the worker is simply just doing their job and their part to expand your growth