@JosephWright Bruno removed the (in the kernel) unused argument from
\tl__act:NNNnn
(now
\tl__act:NNNn
). That argument might not have been used, but it could be used to pass information through to the functions of the first three arguments (e.g., done in my
PR #722). That commit did make
\tl__act:
faster, but reduced its versatility (though it's not currently used in the kernel).