has left me a bit loss, since I'd consider sentience and consciousness to be synonyms.
Historically the two have been considered as separate, consciousness being the ability to be aware while sentience is the ability to feel. The former is more a matter of identifying and cataloging while the later is more a matter of making value judgements based on what is catalogued and identified.
There is a question often brought up in studies of whether it is possible to be aware of things and still not be conscious of them.
An example is that Watson can identify and catalogue which flavor ice cream sells the most but not which tastes best, which treatment regimen reports the least side effects but not which hurts less, which popular song gets played most but not which popular song sounds best.
Anyone so limited that they can only spell a word one way is severely handicapped!