Import 3D comments and walkthroughs from a previous model oin Modelo so ythat you don't have to recreate them again.
When upload a model, check the option to "Import comments and animation from..." and select a model with 3D comments; the new model will have all the comments from previous model, in same position. This way, you will no longer need to worry about lose all your comments when you upload a updated model.
P.S. This feature only supports models uploaded after Oct.31.2016.