Q: “Help! I just want to friendship Anders, but I’m in Act 2 and it’s triggering his romance scene. Am I stuck unless I pick a really messy breakup?”
A: No you’re not stuck, and this is completely fixable.
If you’ve triggered or flagged a romance with Anders and you change your mind later, you can still steer the relationship to a non-romantic friendship-route even if you’ve given lots of flirty or romantic responses previously, and you can do so even late in Act 2, without ever picking a broken heart icon, and without any penalty or rivalry gain.
Passing this along for anyone else who wants to know. Thanks, impressioniste!