Do TRS connectors short adjacent contacts during insertion?
Quoting Wikipedia:


  Heavy-duty  1⁄4 in loudspeaker jacks are rated at 15 A maximum which limits them to applications involving less than 1,800 watts.  1⁄4 in loudspeaker jacks commonly are not rigged to lock the plug in place and will short out the amplifier's output circuitry if connected or disconnected when the amplifier is live.


And:


  A disadvantage of using phone connectors for balanced audio connections is that the ground mates last and the socket grounds the plug tip and ring when inserting or disconnecting the plug. This causes bursts of hum, cracks and pops and may stress some outputs as they will be short circuited briefly, or longer if the plug is left half in.


So, yes.

Also, about standards:


  Due to a lack of standardization in the past regarding the dimensions (length) given to the ring conductor and the insulating portions on either side of it in 6.35 mm ( 1⁄4 in) phone connectors and the width of the conductors in different brands and generations of sockets there are occasional issues with compatibility between differing brands of plug and socket. This can result in a contact in the socket bridging (shorting) the ring and sleeve contacts on a phone connector, or where a phone plug is inserted into a two-conductor TS socket in some cases the intended 'sleeve' contact in the socket making contact with only the 'ring' portion of the plug.


So, unless you can control what kind of plugs are going to be used, I wouldn't be too optimistic about standards as well.