Guest: "Never been to keen on bad punctuation and grammar" apart from the earlier correction of to/too, that sentence appears to lack a subject, as do the preceding three sentences.
Of course, your comment could be construed as meaning:
(I've) never been too keen on bad punctuation; and (I've) never been too keen on grammar.
The qualifier 'bad' might only relate to the one object noun. In which case I would agree that you've never been keen on grammar!

Nigel