Complex numbers in the form of a+bi or a+bj displayed in Calc are poorly readable, although this is not a bug. A special format with different colors for the real part and imaginary part will help to improve readability. For example, blue for real part, and red for imaginary part.
I'm going to mark this as NEW but I'm almost positive that I've seen a duplicate of this one at some point. If someone comes across it please mark this as the duplicate as the other bug was reported against an older version of LibO. Leaving priority as is