How to say something like "I am the man who wrote you a letter"?
Specifically, I'm having trouble with "I am the man who...". {mi
nanmu} means for me "I am *a* man", and anyway, I don't think I can
attach a {poi}-phrase to that. And {mi du le nanmu poi pu te xatra
do} sounds malglico to me.
I am a prime opponent of "du" in most cases. However, when there are two
descriptions that yield "known" entities, and you wish to express the
*claim* that they both actually identify the same entity, then it's
valid. The case I think of as a good example is "Clark Kent is Superman"
(to the people who know Clark Kent and also know Superman). I think it is
valid here for the same purpose.