bash - Taking a Column of Output from comm Without Losing Blank Lines -

i'm trying assemble list of software installations per user. have complete list of users in file1.txt, , list of users software installed in file2.txt. want end lines in file1.txt or in both file1.txt , file2.txt, including blank lines. so:

file1.txt

bhope bsmith fjones jdoe zdirks 

file2.txt

bhope jdoe zdirks 

i can partway there comm -2 file1.txt file2.txt, gives me:

<tab>bhope bsmith fjones <tab>jdoe <tab>zdirks 

i want output be:

bhope <blank line> <blank line> jdoe zdirks 

with bonus points replacing actual output lines "y"'s:

y <blank line> <blank line> y y 

but can't find way preserve blank lines cut or awk.

assuming have fixed sorted problem:

comm -2 file1.txt file2.txt | awk -f'\t' '{print (nf==2?"y":"")}' 

y   y y