The RSK Mk3 has a half guard for the same reason I prefer a half guard of some sort on all my knives, safety. EOD

I have never found a well-designed half-guard to create any problems using the knife.

Whether one believes a guard of any sort is a good thing, a bad thing, right or wrong, or simply irrelevant, is a personal choice. For survival use *I* prefer to err on the side of caution and safety. YMMV

The following comment is not directed at you, but in regard to some of the posts in this thread, and much of the discussion on the forum. Whatever you believe does NOT make you right or others wrong. Arguing for your point of view is good. Implying or suggesting others are wrong, stupid or otherwise ill-equipped if they disagree, is not appropriate. A wee bit of tolerance and adherence to our Rules and Courtesies and participating in civil discourse in this regard would be appreciated. Let your arguments be persuasive in and of themselves.