TTT: Turing Text Tape
Python 3, 157 bytes

t=i=0
p=o='PLEASE'
for c in input():i+=1;k=int(f'{ord(c):08b}'[::-1],2);o+=i%4//3*p+f'DO,1SUB#{i}&lt;-#{t-k&amp;255}';t=k
print(f'DO,1&lt;-#{i}{o}DOREADOUT,1DOGIVEUP')

Try it online!
This prints \$n+3\$ instructions, of which \$\left\lfloor \frac{n+5}{4} \right\rfloor\$ are polite. That ratio just barely fits in the \$[1/5, 1/3]\$ politeness interval for all \$n \geq 1\$.
-1 byte thanks to Neil.