Seems to me the best way to do this is as follows: Define a two fields:
Comment -- Text
Full Comment -- Calculation: If(IsEmpty(Comment),"",FirstName & " " & Comment)
Use the Comment field on your layout, with a pop-up menu, to choose the comment, but make it non-printing (cmd-option-T); put the Full Comment field on the layout wherever you want it to print. If nothing is selected in the Comment field, the Full Comment field will be blank. If you want to use a custom comment, just enter it into the Comment field manually.
At risk of stating the obvious, all the comments must be formatted to make sense with the student name at the beginning ("I really enjoyed having such-and-such in my class" will not work).
Bon chance