The rule (I find just absurd) forbidding any user to comment if its credit is lower than some_value_I_do_not_remember leads to some inconvenience at least in one particular case we can discover in this question :
user Foobar offers a bounty on another user's question, incidentally bringing their credit under the commenting privilege threshold and consequently depriving them from any possibility to interact with the authors of the question / answers. (apart from posting answers that are not answers).
I'm afraid that asking for dropping the condition for commenting is just a lost cause… so, could, at least, an exception be made, to the benefit of the user having offered a bounty for the time the bounty is opened ?
EDIT after acknowledging terdon's arguments :
Limiting the value offered for the bounty to user_reputation - commenting_privilege_threshold could most probably be simpler to implement than an exception while preventing users to inadvertently deprive themself from an important privilege.