Really ?
I tried this tactic against the lunatics near tchort institute in dominating, and i'm pretty sure i broke line of sight for at least 4 turns hiding in a shop after killing a guy from afar, yet i couldn't end combat mode and they eventually found me with seemingly perfect knowledge of my position.
But i'll do other tests when i can, if breaking line of sight for 2 or 3 turns is really all that it takes it will have a huge impact on my way of playing and makes stealth even more powerful !
Thanks to both Styg and Tygrende for answering
Edit : oh i think i get it thanks to Tygrende : you have to break line of sight for multiple turns WHILE being in stealth right ? What i did was going in stealth mode AFTER breaking line of sight for multiple turns.
Pretty cool yet somewhat hidden feature ! I played hundreds of hours without ever noticing that