Thanks! Good to know, I wasn't sure if it could hurt the value. The backs also have ink spots/smudges, they were probably piled up right after signature/numbering. Up until a few days ago, I wasn't even aware of the differents colors/numbers combinations... I was sure all #1s were blue, #2s yellow, etc. Didn't even know up to which issue there was.
Those are probably the most "desirable"/"valuable" comics I still own (across all titles). I have other good pieces: I once attended a ComicCon in Montreal where Sam Kieth met fans and signed art, and got a few issues and trading cards signed (Maxx #1 to #19, 1/2, #1 GITD, Darker Image #1, among others). I place the date around 1995 because that's when #19 was published.
Sadly I was a super shy teen and had pretty basic English skills at the time (I'm French Canadian), so we couldn't quite talk... But I remember him as a very humble and simple person.