nothing is rubbing on the frame even though it looks like these areas have been polished by something

what is it by rOcKeTdOgUk, on Flickr

bike is always run like this, nothing touching the down tube

The Bridge, Tibberton by rOcKeTdOgUk, on Flickr

tears of the clown riding it?

My vote goes to the clamp on a roof/towbar bike rack.

Trouser leg or shoe laces flapping around?

Lock or bike rack

Sweat or bike carrier.

tuck it in?

(or bike carrier)

you’re right, thinking about it, it’s been on mate’s roof rack carrier about 4 times, mine is towbar and doesn’t clamp there, his does, phew!

alien abduction would seem a more plausible explanation to me..

Bike pixies 😆

Nah, it’s obviously the ghostly fingerprints of your cycling weakness clinging on in desperation…