If auto ignition is a concern, I'm confused why venting is recommended (or rather, why flaring is not recommended) as this would seem to be a guaranteed source of "delayed ignition." Given the low ignition energy requirement for hydrogen, wouldn't the likelihood of delayed ignition be significantly smaller for flare stacks with a pilot (e.g., propane pilot, piezoelectric, etc.)?

Rupture discs open very rapidly. Historically, rupture discs opening at high pressure (1000 psig and above) have caused the most damage due to deflagration/detonation. Timing a rupture disc would not be possible. Additionally, how would you have a pilot light on a moving tube trailer? Even with a pilot light at the end of the stack may blow out due to the initial high velocity.

See questions #71 & #72 from Venting for Gaseous and Liquid Hydrogen CHS Webinar Q&A