Hi!
Sometimes, when writing large equations, the rule of adding spacing to all binary operators can lead to a very verbose text. Compare, for example:
aux_U += P[n + 1, m + 1] * (C[n + 1, m + 1] * cos_mλ + S[n + 1, m + 1] * sin_mλ)
aux_U += P[n+1, m+1] * (C[n+1, m+1]*cos_mλ + S[n+1, m+1]*sin_mλ)
IMHO the latter is much more readable and understandable because the spacing is used to separate the factors.