Light theoretically would travel at c in a vacuum, but I think a vacuum is practically impossible. So light doesn’t ever travel at lightspeed? And therefore it does “experience” a tiny amount of time between emission and absorption/reflection?
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If the average density of the medium is low enough, and the wavelength of the light is short enough compared to the average distance between electrons that make up the plasma of the interstellar/intergalactic medium… it shouldn’t provide any overall impedance that would lower the speed of light. You would probably model it over a long distance and take the occasional interaction into account, but between charges the light should be moving at c or *very* close to it.
The second part of your question is more direct, no, light is always moving at the speed of light, even when that speed isn’t c for a given medium. If you want to think about something nonphysical like a photon’s perspective, it would always be the same.
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