Hi, today I have updated assets.dta with the download script,
and I noticed that the new Comm field has value between 0.6-0.8 for the currencies,
should we blank this field instead?

The content of Assets.dta needs not be modified. But you might want to set it to zero in AssetsFix.dta when your broker charges no commission, and to the roundturn commission per 10,000 units otherwise.

Pls Double check, do you mean 10,000, or 1,000?
The first or second column, in this table
http://www.fxcm.com/forex/forex-pricing/

10,000, the second column. All costs in the Assets files are per 10,000 Forex contracts.