The manual says:
Some kinds of display specifications specify something to display instead of the text that has the property. These are called replacing display specifications. Emacs does not allow the user to interactively move point into the middle of buffer text that is replaced in this way.
Yet, if I replace part of a buffer with a string:
(put-text-property start end 'display string)
then cursor movement does not go into the replaced part, but isearch does, though isearch is also an interactive command. Is it a bug in isearch?