I suppose if the target audience of this application is "st0p", then you'd be correct. The rest of us don't necessarily get the luxury of choosing what sort of sense of humor our employers have.

I'm also occasionally aware of how others build their concept of me. If someone had known me for years and I recommended this service, I can't imagine it would make any difference.

If we'd had only incidental interactions, this could easily remain the first thing that pops into their head when they think of me in the future. I worked once in the same company as a talented designer who told a hilarious but quite scatalogical story at lunch one day. That's still the main thing that pops into my head when I think of him. I don't know that it'd stop me from recommending or hiring him, but it remains a significant part of how he's defined in my head.

I'm not sure if this makes me seem like a wet blanket, or overparanoid -- my real point is that I have quite a few different filters, and for most parts of my professional life "fart" doesn't make it past at all.

You can perfectly be unpolite trying to be humorous with this kind of joke.

The easy joke is not necessarily polite and is usually unintelligent: so it is a way of telling the other part "look, laugh at this silly thing" when actually one ought to be able to say "look, laugh at this intelligent joke".