Since facilitators are full members, they should not hold back at all, or their voice as circle members will not be heard. What’s important to alleviate the position of authority that some see facilitators in is to separate member voice and facilitator voice, e.g. by putting oneself in the middle of the round (instead of beginning or end of the round), or by clearly stating from what role they are speaking.
For more information, check out our handbook Many Voices One Song section 5.5.3