I can't claim to "know this language." I did do a very little 8086 assembler way back when, way before there was any talk of "32 bit." But from what I've read, I'm pretty sure it is not used in the kernel except for possibly very special cases of when the kernel is starting up or shutting down. (I have an old machine where I had to specify the kernel go into 16 bit, aka "real mode" before it turned the computer off. Otherwise, because of a BIOS limitation, the computer crashed instead of turning off!)
"Real mode" (a misnomer if ever there was one -- unreal mode would be more accurate!) is basically the old 8086 architecture. It is, IMHO, a horrible architecture that should never have been created. It is incapable of most of the things you take for granted, such as one process not being able to access another processes address space. And addressing is limited to 64K (yes, kilo) chunks defined by "segment registers." Study it if you like, but these days it is probably only used in these very limited circumstances.