There is something odd/wrong in the software here. Initially, I could not get:

IF Genre=[anyvalue]
SET Comment=[tag]Batchname[]

to work.

However, after several edits, i.e. creating/editing the Batchname tag using Edit ID-Tag and the different scenarios described earlier in this thread, I now have this working every time, post rip, using the ID Tag Update utility codec>Rule Based Manipulation.

As yet, I don't why, sorry.