How to properly denote imaginary magnitudes of vibrational frequencies Vibrational frequency computations provide the magnitudes of vibrational frequencies for each vibrational mode of a molecule ($3N-6$ degrees of freedom for non-linear molecules and $3N-5$ for linear molecules).  Sometimes these magnitudes can be non-real (i.e. imaginary).  This is common when characterizing a transition state which contain one, and exactly one, imaginary mode of vibration.

Some popular software packages will print these magnitudes as a negative number.  This syntax has unfortunately propagated itself into common, everyday practice even if technically incorrect.

My question is, what is the best way to denote these imaginary magnitudes, especially in the context of a peer-reviewed journal?  Should we stick to using the minus sign convention (e.g. -15) with a note explicitly defining the meaning of the $-$ sign,  or should they simply be listed with an $i$  (e.g. 15$i$)?

(I've just been told to NEVER use the minus sign convention as this will incur the wrath of the reviewers.  Please feel free to verify.)
The suffix i to the positive wavenumber to denote an imaginary frequency is seemingly accepted by reviewers, see Photochemical transformations of 5-methyltetrazole. Matrix isolation FTIR and DFT studies as one example I could find in a very quick search.