I don't know if anyone has noticed this bug but if you create an artistic text letter R,B,P,D and convert it to curves to create a vector object. Then clone that object with a CTRL drag. Select the cloned object and flip it horizontally. Then bring them together, so the stalk overlaps to give a mirrored, merged effect. Then select both images and use the geometry add function, the objects do not join as expected. The one on the right fills in the hole in the R, B, P, D but leaves the object on the left as is.
I have included a document for you to try and replicate this for yourself. The object on the left is what the add function should do (created in DrawPlus). All you have to do is select both of the objects on the right and select geometry add function.
This bug also occurs in Affinity Designer.
Geometry bug.afpub