In P&P all clerics get a bonus language, regardless of alignment. The 3.5 handbook says it's a choice between celestial, abyssal, and infernal, but it would be cool if draconic and sylvan were also available. Draconic would be a great pick as a cleric of Mystra or Azuth, and sylvan would be great for people who worship a fey or nature deity.
A way this could be implemented is after X number of cleric levels, they could get a bonus language in a similar way as Loremaster where you get a prompt in the combat log saying you get a bonus language and type -bonus_language to pick it.
I'd leave it not alignment restricted and let people pick whatever they want. In a previous thread, an underdark player said not speaking abyssal was a way that was used to out non-evil drow clerics. While the given example was a CN Lolthite, clerics of Eilistraee suffer similarly. As well, there's good and evil feyish things people can worship.
