@anna I'm not sure that it's possible for an event like FOSDEM to change in it's essential form.
Not with it's history and not with the current organisers. FOSDEM resisted having a robust COC for years.
We're going to find this with established tech events, who have always catered for the audience they know rather than the wider community.
So perhaps the answer is to organise new ones, this is why events like FOSSY and North Bay Python are awesome.