Riding instructors, Police, Blood Bikes, Couriers, Ambulance Bikes, all professional riders, and they ALL filter.
As do I and, from the looks of things outside, I'll be filtering ALL the way home down the A33 tonight...
I'm not
AT ALL saying it should never be done - Just the opposite. But the fact remains that it is FAR more dangerous than sitting stationary in traffic and you're FAR more likely to have an accident while filtering or overtaking, than to be rear-ended by another vehicle.
Anyone come off while filtering?
Not me, but seen several riders go down when cars and passengers have either opened their doors or purposely pulled across to achieve such a thing. Had one subsequently get out the car and have a go at this poor downed rider, because he was adamant that bikes filtering were illegal - We re-educated him.
Ain't you legally supposed to stay within the white lines when filtering though?
Nope.
If you're going down the right side of traffic in the oncoming lane, that is overtaking.
If you're going down between two lines of traffic, that is filtering. So when filtering, you are always going to be on/around the white lines of one lane or another.
As mentioned, both are treated as overtaking manoeuvres, unless you're going above the speed limit, in which case you're now undertaking the right-side traffic and thus actually breaking the law.