Hondata

It is my understanding while the ecu is in closed loop it will automatically adjust for fuel except for when you are in a wot mode.

If this is true why should I bother adjusting for fuel if the ecu will effectively do it;s own thing.

You still need to tune it properly to that it is running close to where it needs to be in open loop.

If the fueling isn't quite right, say up to +15% short term fuel trim, what problems might this cause? I've read people say short term should be about 5% or less

If it is off by that much then you should adjust the fueling to get it closer to 0.