My view is that making an edit while respecting the intent of the original author is preferable.
It produces the best and quickest outcome, with the minimum amount of noise and effort required from others.
In this case, GROUP BY should pretty clearly be PARTITION BY so an edit would be nothing but helpful.
Once the edit is made, the existing comment can ...
Until a user has earned the Edit Questions And Answers privilege, suggested edits need to be at least six characters, and preferably many more than that. This may seem like an unfair restriction, but we want people learning to use the site to follow the advice in Why can people edit my posts? How does editing work?
Edits are expected to be substantial and ...
See also answers on the CAPS COPS question. TL;DR: making things better is generally OK; just making things different, not so much. Be sensitive to the intent of the question and whether layout, indentation and capitalisation could be germane.