I think the issue is less coding and more worries about functionality. See, we have sort of a case study for how this would work – Suggest Edits, on entries. Some recent examples of this are:
"Just wondering if you have a way to get in contact with him?"
"any"
"[copypasta about how grandpa died from smoking and the person promised to never smoke and how they got cancer anyways from that page]"
"Can someone finish this please? :)"
"oy gevalt"
This isn't to say all or even most of these are like this. In fact, I made 3 edits to entries based off of the list of suggestions entry mods can access while gathering these up. But this is just to point out that if a little-used feature on a site is abused like this, how will report buttons on comments?
I already get PMs every now and then for comments that I just can't act on, even if I want to. Other mods get them too. These are just people who are aware of active moderators – the entire userbase will have access to the report button. So many reports, I can guarantee, will be a waste of time. And I can guarantee as a result of that, the mod team will be seen as useless or horrible – because we won't act on all these many junk reports that other people think are worthwhile. We'd even likely miss some valid reports, based on how the entry suggestions go – moderators in general don't read the entry suggestions page, as most of them aren't something worth doing something about. For example, one which just said that it was wrong, without actually providing any real correction.
So, to recap:
- It'll be abused
- It'll be ignored because of this
- Mods will be seen as junk because they aren't responding to all the many junk reports and also miss real ones
This idea would need serious polishing to actually work, based on what we have seen happen already.