I can right click on the column name to bring up the properties.
Click on Remove and nothing happens (or click on apply after clicking remove - nothing).
Or bring up standardize attributes
Click on remove and nothing again happens.
Spec limits have not been removed....
The only way it seems to work for me is scripting...
E.g.,
dt=current data table();
Ncols= ncols();
for (i=1, i<=Ncols, i++,
colx = column(i);
colx << delete property ("spec limits");
);