Do bonecharm traits stack?
They all stack (which is also the purpose of and idea behind Trait Synergy).
There have been bugs, like with Strong Arms, where the effect would actually worsen and reverse, but (most of) these have been fixed with updates.
Of course, the same applies to Corrupted Charms, in which case an effect can diminish another or cancel it out (e.g. Armored Bones and Zephyr: reduced movement speed combined with increased movement speed).