Here is the second interesting thing I had happen to me with villagers and nether Portals:

So i don't have pictures (I uploaded them but something weird happened and now I can't access them) to show exact cords of the portals so I'll use examples 

N=Nether

O=Overworld 

1N is linked too 1o

2N is linked too 2o

1N cords= x:100 y:100 z:100

1O cords = x:800 y:100 z:800

2N cords = x:300 y:150 z:300

2O cords = x:2400 y:150 z:2400

(Again I know it's not exact cords but this example show kinda the same space as the portals in my world so it's not prefect but gets the point across)

I was transporting 2 villagers, (leads with boats) I went through 1O with both villagers and they both went through just fine, no hiccups, so I lead both the villagers at the same time too 2N and unattached one and pushed it through, out of the boat, went through the portal myself too 2O and the villager was there everything was fine, trapped the villager and kept it safe. Went back through the portal into the nether and the other villager was where I left it, so I destroyed the boat it was in and pushed it through 2N and went through. Here's where things get alittle funky, when the chunks were loaded, I expected to see 2 villagers at 2O, but there wasn't, there was 1, the second one wasn't there, so I was bummed cause I thought I lost a villager, but lucky I had backups just in case something bad happened to one of them, so I went back through  2O, out 2N, back to 1N to go out 1O, BUT when I went through 1N our to 1O, the missing villager was there parading around like nothing happened! It teleported to the wrong portal!