[pm2222]

Doesn't work here.

  ALARM ~ $ tracepath 2001:bc8:3eff:c0::ff
   1?: [LOCALHOST]                        0.015ms pmtu 1500
  ...
  ...
   2:  ALPHEUS-COM.edge1.Washington1.Level3.net             15.966ms 
   3:  ae5-3828.edge1.Washington1.Level3.net                 4.011ms 
   4:  2001:1900:2::3:18                                    77.693ms 
   5:  2001:1900:5:2:2::4a0a                                78.469ms asymm  4 
   6:  2001:bc8:400:1::8a                                   78.737ms asymm  7 
   7:  2001:bc8:400:1::13a                                  78.635ms asymm  6 
   8:  no reply
   9:  no reply
  10:  no reply
  11:  no reply
  12:  no reply
  13:  no reply

[aidenn0]

I suspect that whatever underlying implementation is used only catches ICMP packets, not UDP packets.

[edit]

Note that "tracepath -m60 bad.horse" works just fine.