I noticed that ObjectTable.Add() does not well maintain the attributes specified in the method if the GeometryBase is a TextEntity. I found out that the originally assigned layer in the ObjectAttributes is replaced automatically by the CurrentLayer. Also, the assigned Name is forgotten. Is that an expected behaviour for TextEntity?
I finally decided to work with ObjectTable.AddText() and it works well. However this makes me raise an exception which I could have avoided with the former method, being more generic.