Gameplay issues are things that subtract stars for me.
Minor typos: 5 stars
Typos that interfere with ability to complete mission (i.e. misnamed system information): 4 stars
"UGC Contacts" instead of NPC names: 3 stars
Grind Mission that takes place in a single spot: 2 stars
In-completable due to getting stuck: 1 star
Lacking Mission Critical Information (i.e. what door to enter): 1 star