about the Final Reflection: Vrenn became Krenn upon joining the Navy, not becoming a captain. Had he gone Marine, he'd hae become Mrenn. Specialists (like science officers) become Arenn.
The sutai-Rustazh (vestai, tai, etc.) indicate social rank and the line one belongs to, but is saved for formal occasions. Thus Krenn, Kang, Kumara, Koloth, Kor for most usage, and the social rank honorific (tai, vestai, etc) and line name combo are not used often.
Some interesting details elsewhere in that post.