I'm not sure if this is an actual bug or simply bad design but buffs/debuffs associated with spells by the player seem to automatically target the player regardless of the spell's type or the actual target of the spell (unless they are set to self="0"?) This makes many buffs/debuffs unusable by modders.
It does sound a bit like bad design. On the other hand, the modder can easily make his/her own copy of the (de)buff he/she wants to use. If the devs change how the spell works in the future, the mod will be unaffected, due to it being a copy, rather than the actual (de)buff.
It is—and was—supposed to work that way. So “bad design” rather than a “bug”, albeit in this specific case I think it is more “misaimed in the long run” than “bad”; they intended for it to work that way because it's easier to set “self="0"” than it is to create a whole new spell just to target the caster, and it is justified but it just so happened that some of us don't like it being that way. Not to mention that originally DoD had no modding support, so it was not a problem back then and it's not like it can be changed on the fly now (it's not all that difficult, but still takes a bit of time). Still, I do get your point. It's just not something I would openly agree with as I do not mind it working that way (nor would I mind it working your way, just to make it clear).
