
Originally Posted by
Hythlodaeus in "A Past, Not Yet Come to Pass"
You needn't be nervous around Venat─those white robes mark her as one of fair and impartial reasoning.
Aside from the emissary, Elidibus, such garb is worn only by those who have stepped down from public office to serve as advisors. Whatever you have to say, she will listen without judgment.
In other words they're not necessarily worn just by retired convokers. At least based on Hythlodaeus's explanation, people of other public offices could wear white robes. So someone with unspecified ties to the Convocation performing an investigation in a white robe might not throw any flags.