D&D 5E (2014) Moonblade properties: do they stack?

[Plaguescarred]

You shouldn't add bonuses from different properties of a moonblade but take the highest one possible only, otherwise it'll reach very high bonuses.



Yan
D&D Playtester

 

[GX.Sigma]

No weapon in the DMG gives more than a +3 bonus (even the most powerful artifacts), and the first rune property makes it clear that the total bonus shouldn't go above +3. So I think it's pretty clear that "functions as" is just supposed to mean it gets the special abilities of the defender (commuting enhancement bonus to AC) or vorpal sword (decapitation), not adding their bonuses.