I want a platform for my site where users can make suggestions on how our organization can improve. This is because good ideas are sometimes lost because the holders of the ideas don't want attention around themselves. This issue is eliminated by having an anonymous platform for collaborative revision and feedback. The QA model with the modifications described in the title would be suitable, I believe. Are there any Open-Source QA platforms that allow such modification? Else, are there other platforms that would satisfy my needs?
Have you looked at Osqa? I've noticed a few sites that have been using it for similar purposes. Out of the box it seems a pretty good stackexchange clone. Given a little styling to look more like a suggestions site and some adjustments to the settings to do things like turn off answers and enable comments only could make it fit your requirements a little better.
The definition of what a "question" means and what an "answer" is, is really up to you. Just explain to your colleagues how to use the system.
Before you get 33 more answers, I'll link to the Meta StackExchange answer for Stack Overflow clones, which is probably the most complete list available so far.
Personally I have Questions2Answer up and running. Installation and setup was very easy, but I couldn't get LDAP to work.
With Talkyard, you can create topics of type Idea. Then, people's replies are feedback and thoughts about the idea. The discussion behaves as in a Question-Answers topic: people reply (post "comments") to the feedback, and a feedback reply and related comments, are grouped together, and the insightful (upvoted) thoughts surface to the top.
Talkyard is open source, GitHub repo; I'm developing Talkyard. Here's a screenshot of an Idea topic:
Once you've started actually implementing an Idea, you can optionally change the status of the Idea topic, to Planned, and then Doing and Done:
... then people will see at a glance (also on the topic list page) that "Oh they've started doing this already".
You can append Progress Notes at the bottom of the page, describing your progress with making the idea happen:
Talkyard supports Question-Answers topics too (there's a per category default topic type setting — e.g. Idea or Question). And open-ended discussions, if you want to talk about news and blog posts.