What users are going to notice? Browsers and almost everything else is going to fallback to TCP and move on, because there are too many broken networks to bother.

Kind of like how most big sites clamp TCP MSS at 1440 instead of 1460; there's too many PPPoE or IPIP tunneled links with broken path mtu, and too many clients without working/enabler path mtu blackhole detection to bother making a fuss about it. Just move on and cry on the inside.