the old post in question
which mention that
ActionScript Inline feature was never completed. As a result, the major ActionScript frameworks such as Starling, Away3D are not taking advantage of the Inline feature.
so yeah a random guy said that it was "never completed", does not bring any examples, does not show anything, and we are supposed to just believe it does not work? please ...
To use inlining, you gonna need to fully understand the ASC compilers, difference between ASC1 and ASC2 and read the following links
Now, if and when your code breaks or does not work anymore, don't jump to the conclusion that ASC 2.0 is broken or not completed
go read again
it is a give and take, you can not have the optimizations of a stricter compiler without following those stricter rules
problem you might encounter is to use a library that does not compile with ASC2
workaround is to compile part of your code with ASC2 into a SWC, and compile all the rest with ASC1