A question about late Roman infantry...

[Robert Vermaat]

"Comitatenses" as in the spatha-equipped Imperial legionary after the reforms of Diocletian (I think) in the 2nd century AD.
I had thought the word was used specifically to describe the Imperial legionary (beside the Limitanei) of the period. Or am I incorrect there?

I'd say not so much Diocletian (late 3rd century) but rather Constantine is credited with the modernisation of the Roman army which produced the more fixed border troops (Limitanei) vs. the so-called 'mobile' field army (Comitatenses).

Comitatenses are equipped liked the Limitanei, although their higher pay would mean in general better equipment. Both could be Germanic volunteers as well as Romans. Both were 'imperial legionaries', equipped with spear, shield, spatha.