Fair points! I'm wondering if there's a way to reconcile the original idea of using the d tag with the use of the d tag in indexing parameterized replaceable events, but that sounds like a dead end.
I'm leaning towards using the title tag for compatibility with other events, like you suggest, and reserving content for a description/introduction.
BTW, how do clients typically generate unique IDs for the d tag? Are they just UUIDs?