For over a year i used reconstruct color without any artifacts .
But apparently , that was luck, because those artifacts are appearing for people quite often I’m told.
In a thread about ‘why is darktable bad in highlight reconstruction vs rawtherapee’ i was of the opinion that this wasn’t the case, because they have the same algorithms. This was WRONG, and a bad assumption by me. In multiple play raw files I’ve encountered files with artifacts like this and even in some of my own shots now. I guess I was always lucky.
(And to be honest , using DxO as a preprocessor removed the need / benefit of highlight reconstruction so I didn’t use it that often ).
So, what you are seeing is (probably ) just something that can happen with ‘reconstruct color’ . Try something else, even if you don’t want to .
(The new hlrecovery segmentation based is a good bet to replace it, try reconstruct lch if you don’t need color in your highlights , or leave it off and try the recovery / smoothing in filmic instead . Specially with luminanceY mode you might get less purple in your highlights ).