If a looping sound is attached to a prim using llLoopSound or llLinkPlaySound, it will not initially play on SL Mobile when these functions are triggered in a script (bad).

However, if the sound was attached to a prim previously using these functions, the sound play for Mobile users on-rez (good, and surprising)! It will also stop when the object is de-rezzed (good).

Buuuuut if you trigger an llStopSound function in a script, the sound will stop for Mobile users (bad).

Also, the sound does not respect calls to llSetSoundRadius (bad). You can set a sound to only play when a resident's camera comes within 0.5m of an object, but Mobile residents will hear it like it's being played at maximum volume from across the room no matter where their camera is positioned.

These issues occur whether the prim is rezzed in-world or as an attachment on an avatar.

I hope that this bug report is helpful and thorough enough.