I wouldn't call that a funny line, especially considering the context of Spellhold.
That's definitely supposed to be a humorous line.
In a mage with PTSD/Schizophrenia is completely within context and tone of the area. It may convey humor, but in reality is actually sad underneath.
The tone of the area is inconsistent. Spellhold is supposed to be an asylum and prison for mages, yet Tiax is parody character. A gnome with illusions of grandeour, never treated seriously by writers in BG1, and BG2 follows on that. Considering Dradeel was a mix of serious and humor in BG1 (his cookbook recipes), interpretations may differ as well.
How come?
The whole theme of the area is insanity and boderline madness which encompasses delusion of grandeur/mania (Tiax), paranoia/PTSD and schizophrenia (Dradeel with his disconnected train of thought and speech). I think it is quite explicit as you go from cell to cell, the different facets of each character and that all of them have madness in common. All conveyed in masterful voice acting with clear variation of prosodia from sentence to sentence. Moreover, just notice the underlying eerie music that establishes the depressing tone. I think it is quite brilliant honestly:
And If you think it is open to interpretation, Irenicus spells out for you
