So I'm not totally clear on what is the actual issue in question here- is it pcs casting the spell in front of guard npcs and running about, or is it just running/walking fast with the speed buffs in the area at all?
I can see an argument for casting spells in front of npcs and getting at least a look. And as someone with a port pc, yes, it can be annoying trying to be an elegant port person and suddenly dirty outlanders (affectionately) zoom past you with no regard for the setting whatsoever, and the npc patrols just... ignore it. And then you have to ignore the guard npc ignoring the dirty outlander (affectionately) pc ignoring the guard npc.
But as mentioned before, running in the public quarter, enhanced or not, is already a fineable offense and that's best handled by gendarme pcs or dms. Though the thought of someone who's racked up such an ocr they're basically attacked on sight all because they run a lot is lowkey kind of funny.
But yeah, fast walking? I haven't seen anyone in port consider that rude or out of line- it's barely commented on, at least from my experience anyway.