It's going to depend. First and foremost I'm not a big fan of such discussions happening in chat at all, to me they always seem better suited to specific site meta as that means whatever outcome there is, it will be available more easily for future reference should that be needed. If you can, make it generic instead of about a specific example too, that way you have something that can be applied to future similar situations, hopefully without rules-lawyering about the situation not being exactly the same.
If whatever post this is about wasn't deleted after flagging it, it seems fair game to link to it, to me. Otherwise, there's a reason users with 10K reputation points can see deleted posts, as stated in the help center:
Make sure what is being deleted should have been deleted, and bring unnecessary or harmful deletions to the attention of the community and/or moderator team.
Just use the 'share' link in such cases, and make sure the unsuspecting user is warned about what they might be seeing. Again, probably best to do this on site-specific meta though, not in chat. Or use the Contact Us option if you think a moderator abused their privileges and you suspect a site specific meta post will not have the desired effect.
If we're talking about stuff that's already been deleted being shared through screenshots, copy-pasting, way back machine, Imgur, Reddit, Twitter, Github Gist or whatever else is out there that allows you to make something deleted visible to everyone again, just don't do it. It only proliferates the alleged violation and will require more cleanup than necessary if the outcome of the discussion is that it is a violation.