[twic]

Sounds like Greg Egan, but I don't recognise that particular story. If you don't get a result here, try a story identification question on Stack Exchange, the residents there are amazing at this:

https://scifi.stackexchange.com/questions/tagged/story-ident...

[purplejacket]

Thanks for that link! There's another old story from a collection I read circa 1992 that I'm trying to chase down ;)