> I don't have any specific need for the alignment of the formula with
> respect to the grid, but I expect the text below the formula to be on the
> grid. However, I've not been able to achieve that with any of the layout
> options described in the latest "details.pdf" manual: in all cases I've
> tried the text below the formula doesn't "sit" on the grid.

Looking through my unread ML mails, I saw nobody answered to you.

Did you try enclosing your formulae in \startlinecorrection ... 
\stoplinecorrection ?
AFAIK that should do the job.

Greetlings, Hraban

Thank you Hraban,

Indeed what you suggest works. If I write:
    a = b + c
the text below the formula is correctly aligned to the grid.

However, what puzzles me is that the version _without_ \startlinecorrection ... \stoplinecorrection works with an old version of context (from texlive 2017). Moreover, i guess this is not something due to my setup, because I observe the same (or at least very similar) behavior in the chapter of the details.pdf manual about grid and math. In the attached screenshot I show the first page of such chapter in the version shipped with a recent beta (on the left) and with texlive 2017 (on the right). While in the old version the text after the formulas is aligned to the grid, in the new version of the manual this is not the case: the text is not aligned.

Is this a known (documented?) change or an unnoticed regression?

Thank you in advance,