I have few problems with the review, I don't think it's fair, and I think my history with utopian has something to do with it.

If implemented, how much impact on the functionality and/usability of the project will this suggestion have?

Negligible added-value to the project / impossible or extremely difficult implementation is required.
the user I've linked to is sending a post every five minutes, receives a down-vote and a comment for every post, that adds up to around 700 transaction per day, implementing that suggestion can prevent 99 percent of that spam. is it really Negligible impact ?
is it really that hard to implement? how many lines of code does that need?

Is the proposal realistic and feasible?
No, it’s impossible or non-cost-effective to implement.
it is impossible to check for the reputation before submitting a post?
how much resources is needed to add a limitation like that, is it more than all of the spam it prevents?

Has the user provided any mockups (illustrations) of potential suggestion implementation appearance?
No, there are no mockups included even though they are needed / No potential solution was presented.
I assumed with a simple topic as "Limit zero reputation users to one post per day" there wouldn't be any need to pad the post with unnecessary images and text. it's a one step process.
if it's a must, add it as a rule, I'm sure people who are after the vote have no problem putting something together to please the moderators.

Has the contributor proposed a possible solution to implement the suggestion?
No, there’s no proposed solution though one is clearly necessary.
I can't get this one, is "Limit zero reputation users to one post per day" not a solution?
or I have to write the code for my suggestion to be a legit suggestion?

Is the suggested feature commonly available in other projects or submitted suggestions?
It’s extremely common and may have been left out intentionally.
does this mean people suggested this before? may I ask for some examples please?
or there's tons of steem like platforms out there already using this mechanism? if that's the case doesn't that mean that it's working and we can be sure that steem would benefit from it seeing it work for others?

As you might already know, I do believe in the idea of utopian and tried my best to improve the quality in the system, however there are flaws and I have even gone as far as demonstrating them once, that might landed me on the wrong side of some moderators but if I made even the smallest change I'm happy with the result, please consider this comment as another demonstration of flaws in the system. I'm not going to bother you with making it a full post.
utopian is becoming another exclusive club for the few who learned how to play with it, people who contribute to open source for the sake of open source have no place in it.