Perhaps code folding.
Code folding is stored as meta-information in PREFDIR, much like breakpoints etc. are. Unfortunately sometimes code folding seems to be incorrectly retained/applied/updated/..., then it appears in unexpected places. I have had this occur with breakpoints.
Solution:
Brutal solution: close MATLAB, delete PREFDIR.
The gentler (untested) solution is to close MATLAB, open MATLAB_EDITOR_STATE.XML within PREFDIR, search for the relevant filename, and then delete the complete FOLD_TYPE element for the relevant lines of code.
