So, if characters @, / and + are reserved, and should always be encoded (or I'm I missing something?) ...
The URI spec states:
"URI producing applications should percent-encode data octets that correspond to characters in the reserved set unless these characters are specifically allowed by the URI scheme to represent data in that component. If a reserved character is found in a URI component and no delimiting role is known for that character, then it must be interpreted as representing the data octet corresponding to that character's encoding in US-ASCII."
Firstly, it clearly does not say reserved characters "... should always be encoded"
For example, if we examine the syntax rules for path we see:
pchar = unreserved / pct-encoded / sub-delims / ":" / "@" and '+' is in sub-delims.
So + should NOT be (automatically) encoded in a path.