Q:

Should close votes require a comment be made? 

It's very easy for a user with a high enough reputation to flag as "on hold".  All it takes is 5 users to make it official. 
I've had several of my (Stack Exchange) questions get put on hold then closed with only one and often zero of the flaggers indicating why they did so. 
Should flagging require a comment be made? 

A:

If a question does not fit one of the pre-defined close reasons

unclear
too broad
opinion based

or off topic reasons

what language next
recommend a tool, library or off site resource
career or education advice

the 'other' option requires a comment be made. 
The first set of three are network wide (though different communities allow different degrees of flex within them). 
The off topic reasons are a distillation of the 'and its not about...' section in the help on topic section. 
Whatever reason something is closed as (be it a network wide close reason, or a pre-defined off topic) there is a explanation of the reason as part of the on hold message.   One could consider this as a "I left this comment" once it is closed. 

Consider the redundancy of writing "This is unclear" as a comment and also voting to close as an unclear question. 
When someone uses the 'other' close reason, that information is changed into a comment written by the first person to close with that custom reason:

Being aware of the network wide close reasons and the site specific off topic reasons should help one avoid asking questions that would otherwise get closed. 

A:

Specifcally to a recently closed question for yours, I voted to close it as unclear when the question was at revision 1. 

In Python, should subpackages have 'test' packages or 'test' packages have subpackages? 
  Which is the preferred test package structure for packages containing subpackages:
Tests in Subpackages? 
  (example)
Subpackages in Tests? 
  (example)
Something else? 

To which you commented:

@MichaelT mattnz BЈовић: you all voted to close this question, but didn't provide a comment as to why.  Please let me know what improvements I could make to help you answer the question. –  Jace Browning yesterday

The close message to the question is the comment:

Please clarify your specific problem or add additional details to highlight exactly what you need.  As it's currently written, it’s hard to tell exactly what you're asking. 

Personally, I don't feel that an additional comment is needed. 
The only answer to the question at this time starts out with:

I am probably misunderstanding the question.  Nevertheless, here is a go.  Please, guide me to the precise question of interest by the means of comments. 

The close reason still stands. 
What is the problem that you are having that can be solved (potentially) with a single answer?  If you are able to clarify it, please note that asking for a range of opinions from people as to which ones they prefer is a poor fit for the Q&A format.