Flew 3/17 DEN-NRT-TPE with NRT-TPE on NH1083. Sat for about 1 1/2-2 hrs at DEN due to aircraft issues, making a tight connection even tighter.
Landed in NRT with 40 minute connection time, made it to bus gate for NH1083 boarding but NH gate agent told all connecting pax from UA139 our seats were resold. Seems to me NH was facing serious oversold, however it was unacceptable to me to be holding a boarding pass on NH1083 with seat assignment and to be told I lost my seat.

Kudos to UA Narita ground staff for getting us out morning after, hotel arrangement and checked baggage handling
.
My question is should I even bother asking for compensation? I would do it in a heartbeat had NRT-TPE been UA metal but I can forsee a situation where UA blames NH for what I experienced in NRT therefore telling me I am not entitled to compensation or also, tells me I should seek NH for compensation.
Believe it or not I don't experience many of these situations (last one being in 2009) so I thought I should ask first before proceeding with seeking compensation.