Yeah I did kind of wonder if names are readily available (as with many industries with name badges) and even announced on the actual flight including the pilots what's the big secret? but I do see why there might be issues as you stated.
It's a shame you can't individually reward service with individual praise. Many companies now go for this faceless 'we work as a team and get praise as a team' mentality which is not fair on those who do more yet get lumped in with others who may not do as much. Much like what has happened with tips in the restaurant industry.
Hopefully Emirates will be able to guess the crew members serving the area from the seat number. It's is a shame that airlines don't take a more personal approach to feedback, it's mostly all-encompassing feedback.
You can praise an individual if you remember who it is
Perhaps if you can remember ethnicity that can narrow down the crew in your cabin by a process of elimination? If it was the SFS/Purser they would have both their first name and surname on their badge, and there would only be 3/4 per plane so that would be pretty easy. Otherwise you're only looking at 7-8 per cabin in J/Y anyway.
Which crew serves which seat number is worked out/assigned by the purser beforehand and not laid out officially/reported back (unless there is a complaint raised - and they get passed down the line much quicker than compliments!) so you may be out of luck because I think it is extremely unlikely that a purser/SFS would remember who was doing what, unless you made a strong impression on the crew.