Very little about Buddhaghosa's personal life can be established with confidence. The Mahavamsa and Culavamsa, the Sri Lankan chronicle tradition that mentions him, gives only a brief notice of his arrival and work, and a much later and more elaborate hagiography, the Buddhaghosuppatti, adds legendary material, including tests of his scholarly ability set by Sri Lankan monks skeptical of a foreign arrival, that most scholars read as later devotional embellishment rather than history.
What can be assessed more directly is his stated method of work: Buddhaghosa presents his major commentaries as translations and reworkings into Pali of earlier Sinhalese-language commentarial material, referred to as the Sihala Atthakatha, said to preserve exegesis going back to the earliest generations of the tradition in Sri Lanka. This creates a genuine evidentiary problem for assessing his originality, because the Sinhalese source material he claims to be summarizing does not survive independently for comparison, so scholars cannot fully separate what Buddhaghosa preserved faithfully from older tradition and what he shaped, selected, or added himself in the course of producing what became the standard Theravada commentarial corpus. His enormous influence on how Theravada Buddhism reads its own scriptures is not in doubt, but the precise relationship between his commentaries and their lost sources remains, by the nature of the evidence, unresolvable rather than merely under-researched.