Filmic RGB with Reconstruction on suddenly 'burns' through managed highlights

Yes, you have made your point and your frustration is understandable. The trouble is, this is a user forum, not the darktable issue tracker (even though developers do hang out here).

To propose/request the change, please use the following link:

Better yet, comment on the already open issue mentioned above:

With enough info and convincing arguments, the developers may take it up(if you are not willing to take it up yourself). Please understand they may decide against it, or may have other properties.

Their solution/workaround was to disable filmic’s highlight reconstruction by default.

You can see that some have picked up the discussion there, prompted by this very topic: