@agramfort  That's a good idea. Do you have something particular in mind or is something like below fine?

    Valid values for mode are:
    --------------------------
    
    mean : Average within each label.
    
    mean_flip : Average within each label with sign flip depending on source
    orientation.

    pca_flip : Apply an SVD to the time courses within each label and use the
    scaled and sign-flipped first right-singular vector as the label time
    course. The scaling is performed such that the power of the label time
    course is the same as the average per-vertex time course power within
    the label. The sign of the resulting time course is adjusted by multiplying
    it with "sign(dot(u, flip))" where u is the first left-singular vector,
    and flip is a sing-flip vector based on the vertex normals. This procedure
    assures that the phase does not randomly change by 180 degrees from one
    stc to the next.

    max : Max value within each label.