The phrase "patches welcome" has come not to be.
Think about it. "You're welcome" itself is always so automatic and impersonal. I don't even say "you're welcome" in real life. I say "thanks" all the time, but never "you're welcome", because you don't care if I do and it's probably not true, anyway.
The phrase "patches welcome" has become like this, too. In fact, it may be worse, because when you do hear it, it's usually motivated by that sort of thing that's just shy of snark. It's the low-hanging fruit of casual dismissals. It's trite.
"Patches wanted" is better to my ear (and eye). It's got a particular connotation, like it's almost a solicitation, and it's more widely applicable because of it; whereas "patches welcome" is almost always a response, "patches wanted" works pre-emptively, too.
- Patches wanted.
- Huh?
- Patches wanted.
- I... I didn't even say anything.
- Yeah, I know. Patches are wanted, though.