I am reviewing pull requests and in some cases when the a bigger change is needed I don't think it makes sense to just add a comment asking the developer to fix something before the pull request is merged/approved, because this way the pull request would be postponed for a long time.
What I am doing is this case is creating JIRAs and I add a comment to Stash and open a JIRA with basically the same information, so I think it makes sense to have these tools integrated.