In reply to UKB Shark:
> Without a crucial peg or two a route will of course become more challenging but what of it? Is there an eleventh commandment that says that “thou shalt never alloweth a route to change”?
No, but...
At the risk of sounding too philosophical, there is a difference between losing something and not having had it in the first place.
What stands to be 'lost', in this instance, is admittedly limited - a small proportion of trad routes that have relied on a 'crucial' fixed gear placement or two that make them relatively safe challenges at a given standard.
But those few cases may be locally significant. Certain routes develop a mythos in the collective imagination as a particular kind of challenge, in much the same way as the broader concept of 'ethics' does in climbing culture. There's a bit of irony if the two things clash, because the value in both is engaging with tradition, playing the game in a way that connects with history and with other gamers.
I'm not trying to present this as the bottom line on fixed gear on trad routes - it's just one consideration, but I don't think it should be ignored. There is value in having ethical consistency, but there is also value in preserving quality in the form of a select small number of routes that can be attempted in good style by more than a tiny number of people.