Since adding objects to lists through scripting is a Very Bad Thing...
Why is that, anyway? I've heard people say this but can't seem to find an explanation why.
The scripting functions to do so were introduced with Tribunal, but people had discovered the need for (and created tools to perform) levelled list merging and sorting before Tribunal came out. When these functions are used, the levelled list so generated is stored in the savegame and breaks levelled list merging. Now if all mods that ever used levelled lists used these functions, there wouldn't be a problem - except that they wouldn't work for people who didn't have Tribunal.
And So The Levelled List Functions were declared a Very Bad Thing not to be used in public; you should only ever use them on a levelled list that is unique to your mod and you can guarantee that nobody else will modify. What you
can do is add a function-managed list as a nested member of a merge-managed list; but be very careful in doing so.
Adding a filled soulgem in such a way will probably cause a CTD :shrug: