Pert, where exactly did I refuse anything in this thread? You may not know this, but that's likely slander.
I am registered and have used some 82 other forums. Except for trying to share things with people, file bug reports, and offer suggestions, I don't like coming using the Arduino forums. While people may offer differing opinions or methods to accomplish programming goals, I feel that there is an undercurrent here of unchecked cruelness to new would-be programmers. I hope that over time that will change because young, impressionable people also visit these forums--and they don't need that. Anyway....
When and if someone chooses to use a single 1-bit variable, on compile-time, the IDE could initialize a table of: variable name, byte, and bit, likely as pointers, but for the course idea is:
variablename, byte, bit
myvar, 0, 0
In the above example, the byte position would be a relative offset starting address from where the compilers would keeping the bit variables.
The compiler would deal out memory in 8-bit or 16-bit int chunks, whichever is more efficient. A maximum byte-bit tally can be kept, so the next table entry lines up to the last, in a similar manner to a filesystem freespace allocation map. Because it's done at compile time, in a static manner fragmentation is not an issue.
Using a single-bit variable would cost in program memory, in the form of a library loaded behind the scenes. In my experience Arduinos have more practical space issues with RAM than program memory.
The loaded library would include small, efficient compact routines to translate the changes to the variable, And'ing or Or'ing them for the user.
In the case of an bit array, the table could be extended to use a bit length, likely confined to a particular size. The table entry would look could this:
variablename, byte, bit, length
myvar, 0, 0, 32, 16
Without the compile-time bit locations, the user would either have to use global variables for it's housekeeping, (which doesn't personally bother me, because I am working on my projects alone, and I enjoy organizing namespaces and structures) or they need to lean toward creating an object-oriented approach, which I feel is too abstracted for efficient micro-controller programming.