[plt-scheme] read doesn't like things commented out with a box

When I use read on a file of Scheme that has some stuff commented out
with a box, I get this:

read: #reader expressions not currently enabled

When the file is saved as text this doesn't happen because of the
conversion of boxed comments to semicolon-prefixed comments.  But
that's a little inconvenient, can it be avoided?  Can one enable
"reader expressions", whatever those are?

Ethan