It's not modal.
But it is annoying.
I couldn't find a way to disable those hints in the Preferences dialog. You can make a request with the team using this form Feature Request/Bug Report Form
Am marking my answer as correct for the benefit of other users with a similar question. Feel free to unmark it if you disagree.
What makes this popup especially silly is that there's already a tip of the day window in the default startup screen. Currently it's hawking the new Camera tool.
The popups are VERY annoying, especially since they partly cover the tool bar and Properties window.
I'm paying for CC, not using a free trial, and I should not be pestered with popups that interrupt workflow!