3.3.4 Errors and optimization
Penultimate para, last sentence: "An implementation, however, may
not raise an error...".  This could be construed "an implementation
is not permitted to raise an error...".  Of course, this
interpretation contradicts the rest of the passage, but it would
be better to reword this, perhaps "an implementation may fail to 
raise an error..." or "an implementation is permitted not to raise
ane error..." or even "an implementation may, however, not raise 
an error".

See also my comment #1603 that the term "may" has not been defined.
If "may" is given its usual definition "permitted but not
required" then your use of "may" in this sentence is actually
correct, although it still reads poorly in ordinary English.