main danger if you would use mounting option "notreelog" which must be avoided in case of external drive. Also using of old Kernel versions increase the risk.
Other significant option for performance and also data safety is:
> commit=number (since 3.12) Set the interval of periodic commit, 30 seconds by default.
So to sacrifice performance but increase safety use "commit=1" in mounting options.
Also I usually add "noatime" if there is no need for such information, which removes unnecessary write operations on file access (read), thus reducing risk.
One more good option is "recovery", which enables automatic recovery in case drive WAS unplugged or just lost the power, or since 4.6, "usebackuproot" which has replaced "recovery".