What if they edited with another program? If they just copied and pasted the text from the terminal, directly to notepad and saved/sent it, then there will be no changes documented. Also, if it is a newer version of office/word, they default to saving in .docx which is xml, which will keep track of various pieces of information (changes, formatting, etc). It is rather difficult to check the validity of logs submitted by anyone.
How about a command to report a person? Not just simply bring that character to the admin's attention, but how about saving (temporarily) a bit of information surrounding the time the report was filed? For instance:
I am running around playing, and I kill a mob another player needs for a quest (lets say I wasn't being malicious, I was just killing mobs for exp/coin/items/whatever). The other player gets annoyed since they have had to wait for a large amount of time on that particular mob's respawn, and begins berating me, I request for them to stop, but they continue, so I just type "report <person>" and it will send a notice to the admins, and create a log file (maybe create a note to admins with the appropriate information in the note body?). The log would contain information from the last X minutes, or the last X commands sent, possibly also the last X commands received (so you can have two sides of the story). That way, noone can tamper with the log, and it can be investigated thoroughly.
Obviously this was just a basic example, and can contain as little or as much information as needed.
The other idea is to create an in-game "log" command for mortals that will "log" their session temporarily , just in case, but does not save between sessions and such.
Just a few ideas, which are much better than accepting player submitted logs. Some players are trustworthy enough as to not modify a log that they are submitting, however they may modify it to remove personal tells, or information that is not relevant, etc.