Interesting. Actors should be able to be in multiple aliases at the same time. Can you give me any more details on what you were trying to do here? Feel free to PM.
I decided to start over with my files from scratch so it took me a bit of time to make sure what was going on was not dirt from testing files.
1) Hellos' and Goodbyes' -> not compatible at all only 1 mods will ever show <- unless there is some way to get these to cohabitate from 2 different mods that know nothing of each others existance.
Note: kinda minor overall but you do lose some quest pretense when your openings' and closings' do not work.
2) AI Packages -> they seem to both apply in some hierarchy for instance I noticed travels will override follows forcing the player to do the travel based quest first -> basically temporally breaking the second until you finish the first.
Also as was mentioned up top priority takes precedence as well so a 70 follow quest will override a 40 travel.
Note: while this is probably the only and best way to handle quests adding Packages to the same actor it would be good practice to wiki document that modders should find a way to see if this actor is already busy with another quest before being allowed to give out another that involves any kind of travel.
3) scripts seem to run in parallel and I think this is where I ran into the odd issues with my previous tests.
ALSO quest TIF_ quest script fragments I have already run into incompatibilities here where 2 mods used the same fragment name and totally borked the quest running....
On a side note to the above I tried to write some basic scripts for quests that did things I will end up doing alot like scn ssGetOwningQuest().SetStage(5,10,15,20,25,30,...->you get the idea) and compiling these then manually assigning them as my fragments so multiple quests would use each script so I could alleviate some of the same name issues but every time I did this the fragments stopped working and upon reloading the mod those fragments returned an error and just did not work -> would there be a way to do this?
Everything else seems to be going very well and I think with a bit of forewarning on the wiki tutorials to help people not fall into some of these pitfalls things will work out in the end.