I listed this bug under Insert, Transform, Scale, Move, as I believe this has something to do with duplicating/copying which Inserts a copy of a different model.
For some reason duplicating/copying instances will add a number after the name. This used not to happen and this affects developers’ workflow. I don’t think this was intended to happen as it wasn’t announced anywhere. I hope this issue can be fixed because this affects the way I work with objects, which shouldn’t be renamed. I have to manually rename them to the original name to make sure they work properly.
Cloning an instance through a script will not cause this to happen.
This is an optional feature! It is part of the next gen explorer beta, which you seem to have on. You can disable it in the three dot menu next to the new explorer.
This is being worked on and soon will not have a space between the number, from staff responses in the announcement topic.
In the meantime, if you want to disable the behavior while keeping the old Explorer, you can temporarily enable the new explorer beta feature, turn off the setting in there to increment names, and then unflip the beta feature, and I would expect it to persist.