Hobgoblins' eye changes based on whether or not it can use Thermal Barrier. I've killed well over 10,000 Hobgoblins and yet not once noticed this small detail until I was just mucking about with the HUD off.
[spoiler]Left: On cooldown
Right: Active[/spoiler]
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Ok so I found out TODAY that you can drive a Sparrow across water. I had no idea before that. I accidentally fell off the Forgotten Shore on the Saber strike and expected my Sparrow to explode in the water but nope.