Also remember that they have an entire ceremony surrounding the death of family members where those who are dying get to unload all their secrets to their family/ friends?
I think this is important because:
1) it is EXPECTED in Cardassian culture to have secrets, to have thoughts, opinions or information that belongs only to you.
2) you are not expected to take that information to the grave. This is probably why assassination is so big. If a person becomes terminally ill then they have a chance to spill their guts free from social consequence.
3) it’s a fascinating concept, I imagine there’s some deeper cultural significance to revealing all your secrets on your death bed. Like it lightens your soul so you can rest peacefully. Might also play a part in how Cardassians don’t allow outsiders to see their dead, like “they are free of the cruelty of life. Nobody and nothing should torment them anymore” something like that?
More evidence that all Cardassians lie and obfuscate:
they flirt by arguing. This is probably because openly displaying affection to a person you aren’t married too could be seen as crass or publicly indecent. So if you argue you can express heavy emotions without saying the quiet part loud. You can say “I think your opinion is utter trite” and what you actually mean is: “I love spending time with you, you make me feel warm and fuzzy inside” again this is lying in every day conversation.
In conclusion, no not all Cardassians lie through every breath, but many do.
I have a strong inclination to believe this is a class thing. The higher on the class ladder you are the more cultural incentive you have to be snake tongued.
For example Garak and Dukat have families from very high Cardassian society. As such the two of them are compulsive liars, not just in truthfulness but to themselves (I’m looking at you Dukat) and as a means of manipulating people around them. Lying to get your way is probably just a basic survival skill for Cardassians from prominent families. Garak being the secret son of the Obsidion Order head just so happened to have that aspect of his culture magnified intensely.
Comparatively if you look at Damar who is more verbally forthright, I get the strong inclination to believe he was born middle class and fought his way to the top. Consider also, he was a man of the people and retained his Legat title even as head of central command and a rebel leader. The fact that he never takes the Gul title tells me that he has humble origins. This all probably explains why Damar is more likely to say exactly what he means.
Mila who is a house keeper is also not a very strong liar, but then again she holds heavy secrets very well. She’s not a liar so much as a steel trap for knowledge.
Cardassian society are not “liars” so much as they are people who speak a different syntax to other cultures. “Darmok and Jilad and Tanagura” style language that communicates more between the lines than through the actual words themselves.
The written script for Kardasi is also extremely visually complex which indicates to me that again, there is more said in what is NOT said.
Thanks for coming to my Ted talk on Cardassian culture, I’m going to go take a shame nap…