The state of Doriathrin, as a language or dialect, relating to Sindarin proper is not fully known. In the annals the names Dolmed, Menegroth, Mablung, Nauglamîr, Dagnir Glaurunga, Thingol, Thuringwethil and Dior refer to names of the speech of Doriath. On the contrary, Daeron is proper Sindarin form of the Doriathrin name Dairon.
In general, Doriathrin seems not to have been derived from Old Sindarin. For example OS *botto (from PQ *mbottô) brings proper Sindarin both; but the same word in Doriathrin is moth so it can't be derived from *botto but from an older form where the m of *mbottô was retained.
Doriathrin also seems to have preferred short monosyllabic words where their Sindarin cognates had two syllables. Doriathrin tended to drop the second vowel. For example: