Final answer:
Steady progression from initial onset is not a clinical feature highly suggestive of multiple sclerosis; MS usually has a pattern of relapses and remissions.
Step-by-step explanation:
The clinical feature not highly suggestive of multiple sclerosis (MS) is a steady progression from initial onset.
MS is characterized by episodes of symptoms (referred to as relapses or flares) followed by periods of recovery (remissions).
While some forms of MS can have a progressive course, it is more commonly marked by a relapsing-remitting pattern.
The other options listed, such as optic neuritis, worsening with elevated body temperature (Uhthoff's phenomenon), fatigue, and Lhermitte's sign, are indeed symptoms often associated with MS.