I was listening to this chorale from Cantata 150 where a chaconne movement takes place:
e I noticed that at a certain point the violins repeat the melismas that the singers previously performed in the inégale manner.
Let's set aside the fact that they don't go together, and that I don't understand why the singers play equable and the strings do not; I wonder if there is a rule in non-French music and, specifically, in an author as linear as Bach. The same applies to the double dot: at the beginning, the first violin seems to want to use it, but then does so for an indefinite duration.
Or perhaps you are saying that, in general, the phrasing adjustment adapts to the needs of the singers, so if for them the tight dot "cannot" be done, then the strings perform accordingly. In this Koopman version, it is much more linear; I would like to hear a different version.
Even in the chaconne for violin, the percussionists are a bit indecisive about whether to tighten this point or not. I even heard a violinist playing the allemande from the second partita entirely inégale, except for the tied notes.
For me, German Baroque is a place of anarchy: since it draws inspiration from French music as much as Italian music, then anything goes!
... and there is also a bit of confusion: some want vibrato, some don't; some want mèsse di voce, and some say they are nonsense (even among Baroque specialists).
This is an example of a violinist who plays without vibrato or almost without it, and without mèsse di voce (meaning they perform crescendos and diminuendos that are always linear based on the harmony). Excuse the recording quality, I assure you that live he was a monster (not just in terms of ugliness):
