Why do we want to mess with the version numbers chosen by mod makers? We should try to present mod version numbers in the same way they are presented in their sources and their forum threads.

FYI, the "2:" you are seeing there is an epoch, and that is a extra element we add at times in order to force correct mod version ordering when mod authors accidentally take their versions backwards. We have a setting to hide them in the mod list, which is on by default. We should hide epochs on the latest version column if we're hiding them in the installed version column.

To add this feature, there should definitely be a option in settings, and it should be off (thus displaying the "v"s) by default.

semver/semver#235

In my opinion the leading 'v' belongs to a tag (e.g. on a git repo) but does not belong to the version string itself

Sure, but how many mod authors are actually following SemVer precisely versus copying what they have seen other people do? For that matter, I suppose I'm not using it correctly on our forum thread.

As an example, check out https://spacedock.info/mod/234 version history. It's all messed up. We're probably going to have to slap an epoch on that mod to get it back into order the next time they change their version string.

Like I said, make it an option that people can turn on if they want to.

We have a setting to hide them in the mod list

then maybe also hide from update or install mods process window?

check out [x]Science SCAN Version Tab - not sure what happens there, but looks like really vV5.13 < v5.14, epoch is needed.
SEP uses v-or-not-v by random, that why 2.1.5 in the bottom.
QuickStart changed author, so v is disappeared and epoch is neaded.

All this wouldn't be there if v is excluded from SCAN in the core... in the some 'Version' core-object ?

#963 is relevant here.

Or, to put it another way, https://github.com/KSP-CKAN/CKAN/blob/master/policy/version-comparison.md

Changing the display of version numbers is ok (as long as we allow people to keep things as they have been in the past) Changing the version comparison in the Core means breaking compatibility.