Can a unit be buffed +2?

No, a unit cannot be buffed +2.

According to Rule 702.3, there can only be one Buff on a unit at a time. Furthermore, Rule 703 states that each Buff individually contributes exactly +1 Might to a unit.

Because a unit can only have one Buff counter at a time, it is impossible for a unit to have multiple Buffs to reach a +2 bonus. If you attempt to add a second Buff to a unit that already has one, the action will have no effect (Rule 702.3.a).