For a Danish dude, you seem to know a lot about Ukraine-Moldova relations.

First keep in mind that both Ukraine and Moldova were under threat from razzia this whole time, so don't expect Ukraine to be very brave on this issue. Ukraine couldn't even remove razzian troops from its own soil (crimea), let alone Moldova. Also I know that Ukraine let's Moldova use a port in Bukovia, and by that it allows Moldova access to naval trade. So I guess Ukraine is not all bad as you trying to make it look.
As for allowing some of Transinistrian separatists to hold Ukrainian passports and refuge on Ukrainian soil, well first the place does have a lot of ethnic Ukrainians, so I can see why would Ukraine allow them access. Also Moldova itself allowed the leader of Transinistria itself a few yeas ago to defect to Moldova (Shevchuk).
This is a complicated situation. It's hard to deal with these kind of regions and their population. For example Ukraine didn't arrest many of its own separatists in donbass and Crimea, and allows a relatively free flow of population from those territories.
Ukraine wasn't a real country in the 90's, so don't expect much from them.