Weird, when I install Kerbal Komets 0.5.0 into KSP 1.3.1 it gives me the "Wrong KSP Version" pop up telling me to use KSP 1.3.
I didn't have a previous installation of Kerbal Komets present to even cause issues.
Wondering if it is just me.
>EDIT
I snooped around and found that the "KerbalKomets.version" file in it's main folder had the KSP version listed as 1.3.0 so I tried just changing that from
"MAJOR":1,
"MINOR":3,
"PATCH":0
to
"MAJOR":1,
"MINOR":3,
"PATCH":1
and it all seems to be working fine