Cross posting is a nightmare for every site. Reddit has an interesting mechanism where it is possible to see all the posts a member on the site has made. I answered a question on Reddit yesterday, then noticed the OP had also posted the same query in another sub Reddit. I was able to go to the 2nd posting and at least leave a message that I had resolved the issue in the other sub.
Yes, posting a link back to another Group or Question where an answer exists is possible. The issue is that this does nothing to reduce cross posting. If anything, it seems to reward the casting of a wider net.
If it is not possible to see all posts a user has made, another option could be adding a line of text to the New Discussion text:
- Make your discussion related to the group theme.
- Start open ended discussions.
- Keep it clear and concise.
- Don't vomit your discussion across multiple Groups by cross posting.
- For more details, read the guidelines.
An image is attached of some random person's recent Reddit activity. A function like this, or a search function in Groups could make it easier to find cross posting. I think it comes down to a desire to prevent such posts, then choosing the method(s) of controlling it: