This paper draws on data used in the pilot application of data-driven pedagogical strategies for dealing with non-nativeness in the writing of advanced FL learners of French to expose attendant practical problems and theoretical issues. The discussion focuses on the question of vagueness in academic writing and involves a three-way comparison of FL French data, NS target language data and NS mother tongue data. This contrastive approach entails assessing the relationship between speech and writing in the diagnosis of sources of non-nativeness, and the influence of both interlingual and intralingual transfer. It underscores the interrelatedness of discourse and psycholinguistic factors generally, and, more specifically, the likely psycholinguistic relevance to questions of non-nativeness and written phraseology of contrasts in cognitive and discourse constraints between speech and writing; it also points to limitations of classroom data likely to be used in pedagogical applications, and suggests that principled guidance from research is needed if these questions are to be satisfactorily dealt with in teaching.