Permissions can't conflict, they are simple additive functions. If you grant someone "edit", then they can edit things. If you grant them comment, then they can comment. There's nothing there to conflict.
In confluence, you can't grant permissions to people without granting them view, so you can't run into problems like "I can create, but not see, a page" (In Jira you can set it up so people can create issues that they then cannot see)
The other one to be aware of in Confluence is that you can restrict individual pages, taking away people's view and/or edit permissions.
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