I've posted a few bottles through ipostparcles and put it as sports equipment not had any issues to date but accept that if found they could possibly be destroyed
The current situation is different to the past
And if you really have posted like that in the past then you're part of the problem
Legislation has changed, and those that will take cylinders thorough the right transport methods but require the regulator to be removed are doing so because of the people who sent cylinders incorrectly declared and even pressurised. Not good if it gets sent by air
Check the prohibited & restricted lists of the carriers and send responsibly