If I read Denny's email correctly, this section is broader than conflict of interest:
I discussed with Jan-Bart, then chair, what is and what is not
appropriate to
pursue as a member of the Board. I understood and followed his advice, but it was frustrating. It was infuriatingly limiting.
E.g. any comment Denny made on Phabricator now being read in the light that he was a board member.
I think one of the learning points (assuming I have understood correctly) is that someone who is great at coming up with ideas and making stuff happen is not necessarily a great fit for the Board. It can actually be very awkward having a great operational/project idea as a Board member as just talking about your cool idea creates tensions. Is your project getting special attention as you're a board member? Are staff spending time progressing things on it because they think it has special importance because you're on the Board (possibly taking away from what their manager thinks are their priorities?) If your cool idea doesn't quite fit with the ED's direction of travel are you undermining them?
That kind of problem shows up regardless of there is a COI or not.
As a result, board members are actually really restricted in what they can personally propose and progress.
There is a natural tendency in the community elections to choose people who have done admirable things but I think this is a case of (among other things) an amazing "do-er" and thinker being frustrated by the implications of being on a governance board. (Not the first and probably not the last time in our movement, I suspect)
Regards,
Chris