Thank you mateshibui wrote:Reverse taper is where you have a thicker area above a thinner part of trunk or branch. Our minds expect a tree to be widest near the ground and get gradually thinner all the way to the top. Reverse taper can upset our unconscious feeling of what is right and proper so we try to avoid it in bonsai.
Your tree is just starting to develop reverse taper where those branches come from. Several branches from one place on the trunk can cause the trunk to swell up and develop reverse taper. My advice is to cut off 2 of those low branches to stop it developing further.
I doubt liquidamber would be grafted. They are so easy to grow from cuttings it would be unusual for someone to graft. More likely to be a root cutting which often look like this and would also explain the reverse taper.
It looks like there is another small tree growing from fa spare root beside the main tree. you could separate them in winter and have 2 trees.

I was thinking about topping her to try and force lower buds... not sure if you guys can see it but looks like 4 tiny buds coming out right at the bottom too so might get them off now
Regards
Wal