I've sat on selection boards as an Assistant Recorder. The briefer for your designator group absolutely reviews everyone one of your graded (i.e., O3) FITREPs. If you have some stain in your write-ups in your FITREPs from O1 - O2, you better make sure you are working to make yourself stand out as a top officer.
During my time as an Assistant Recorder I've read well over 1,000 FITREPs. And yes, many, many CO's really suck at writing FITREPs leaving the briefer to wonder what the hell the CO was trying to convey.
Take charge of your FITREPs and write ups. Make the CO's job easy. If you submit a draft write up for chop that says you are the second coming of [deity], and the CO signs it, good for you
FITREPs are written in a vacuum and boards do not verify anything in the write up. I've seen some doozies.