Genuinely baffled about the heavy-breather-wanking thing. You can't see them, can't be sure they're there, for all you know they only exist in your imagination. The only reason that could be bothering anyone is if they made a conscious effort to think about them. WHY would you do that to yourself?
Anyway, for my sins, I spent a couple of years of my life working in an office that dealt, among other things, with legal issues relating to the protection of children. In the course of that, I got a fairly clear look at what the genuinely creepy are into. So, if you want to really avoid threads that someone might be masturbating over, stay away from anything discussing lower underwear, socks, shoes, stockings, tights, prolapses anywhere south of the navel, feet, any kind of body hair or odour, or anything anyone female might do while sat on the lavatory, particularly if it happens other than on a lavatory or while fully clothed.
Slightly lesser risks include gloves, bras, corsets, hair and the styling/brushing thereof, getting muddy, sweating, laundry, getting spattered with food, and blowing up, popping and handling balloons.
Your actual wankers are almost certainly not on or provoking the sex threads. Those that want that find themselves entirely well-served on the rest of the internet, often in HD video. It's the 'specialty interests' that have to go looking on sites like this one.
(Full disclosure: I tend to go wandering down memory lane for the rare occasions when I want to crack one off. Generally women are not involved. Or, on some of the wilder occasions, even in the building. 
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