user21281: The Portable Game Notation (PGN) specification appears to contradict itself regarding the valid characters that may appear in a symbol token.
From [1], section 7, quote:

A symbol token starts with a letter or digit character and is immediately followed by a sequence of zero or more symbol continuation characters. These continuation characters are letter characters ("A-Za-z"), digit characters ("0-9"), the underscore ("_"), the plus sign ("+"), the octothorpe sign ("#"), the equal sign ("="), the colon (":"), and the hyphen ("-") ...

Or, to put it more concisely, a symbol token conforms to the regular expression /^[A-Za-z0-9][A-Za-z0-9_+#=:-]*/.  
However, this definition explicitly precludes the game draw termination marker 1/2-1/2.  Quoting again from [1], section 8.2.6:

Each movetext section has exactly one game termination marker; the marker always occurs as the last element in the movetext. The game termination marker is a symbol that is one of the following four values: "1-0" (White wins), "0-1" (Black wins), "1/2-1/2" (drawn game), and "*" (game in progress, result unknown, or game abandoned).

The string "1/2-1/2" very obviously does not meet the definition of a symbol token, so either:
a) the solidus character ('/', 0x2f) should have been included in the definition of symbol continuation characters, but the author failed to do so, or;
b) game termination markers should not be considered symbol tokens, but rather a distinct type of token which is separate from symbol tokens, and the author failed to indicate this, or;
c) I have completely misunderstood the wording of the specification, and am an idiot.
Somebody has screwed up here, and either it's me, or it's Steven J. Edwards.  Hopefully it's me.  Personally I think (a) is the most likely of the three but perhaps I've missed something.
[1] http://www.saremba.de/chessgml/standards/pgn/pgn-complete.htm

user17425: I agree the spec is ambiguous.  This antlr grammar uses your option b

game termination markers should not be considered symbol tokens, but
  rather a distinct type of token which is separate from symbol tokens,
  and the author failed to indicate this

In the grammar I find 
SYMBOL
: [a-zA-Z0-9] [a-zA-Z0-9_+#=:-]*
;

separate from termination
game_termination
 : WHITE_WINS
 | BLACK_WINS
 | DRAWN_GAME
 | ASTERISK
 ;


user924: You are right, the text as written there isn't exactly correct.
It also says that the marker is a symbol and lists * as one of the options, even though * is a token on its own and also cannot occur in a symbol.
That said, the meaning is clear enough, 1/2-1/2 is a valid termination marker. How you solve this in your code is up to you. As it's hard to add 1/2-1/2 as a token on its own (would need lookahead to disambiguate it from symbol 1 et cetera), it's probably easiest to add '/' to the possible symbol characters, yes.

21281: <p>The Portable Game Notation (PGN) specification appears to contradict itself regarding the valid characters that may appear in a symbol token.</p>

<p>From [1], section 7, quote:</p>

<blockquote>
  <p>A symbol token starts with a letter or digit character and is immediately followed by a sequence of zero or more symbol continuation characters. These continuation characters are letter characters ("A-Za-z"), digit characters ("0-9"), the underscore ("_"), the plus sign ("+"), the octothorpe sign ("#"), the equal sign ("="), the colon (":"), and the hyphen ("-") ...</p>
</blockquote>

<p>Or, to put it more concisely, a symbol token conforms to the regular expression <code>/^[A-Za-z0-9][A-Za-z0-9_+#=:-]*/</code>.  </p>

<p>However, this definition explicitly precludes the game draw termination marker <code>1/2-1/2</code>.  Quoting again from [1], section 8.2.6:</p>

<blockquote>
  <p>Each movetext section has exactly one game termination marker; the marker always occurs as the last element in the movetext. The game termination marker is a symbol that is one of the following four values: "1-0" (White wins), "0-1" (Black wins), "1/2-1/2" (drawn game), and "*" (game in progress, result unknown, or game abandoned).</p>
</blockquote>

<p>The string "1/2-1/2" very obviously does not meet the definition of a symbol token, so either:</p>

<p>a) the solidus character ('/', 0x2f) should have been included in the definition of symbol continuation characters, but the author failed to do so, or;</p>

<p>b) game termination markers should not be considered symbol tokens, but rather a distinct type of token which is separate from symbol tokens, and the author failed to indicate this, or;</p>

<p>c) I have completely misunderstood the wording of the specification, and am an idiot.</p>

<p>Somebody has screwed up here, and either it's me, or it's Steven J. Edwards.  Hopefully it's me.  Personally I think (a) is the most likely of the three but perhaps I've missed something.</p>

<p>[1] <a href="http://www.saremba.de/chessgml/standards/pgn/pgn-complete.htm" rel="noreferrer">http://www.saremba.de/chessgml/standards/pgn/pgn-complete.htm</a></p>
 17425: <p>I agree the spec is ambiguous.  This <a href="https://github.com/antlr/grammars-v4/blob/master/pgn/PGN.g4" rel="nofollow noreferrer">antlr grammar</a> uses your option b</p>

<blockquote>
  <p>game termination markers should not be considered symbol tokens, but
  rather a distinct type of token which is separate from symbol tokens,
  and the author failed to indicate this</p>
</blockquote>

<p>In the grammar I find </p>

<pre><code>SYMBOL
: [a-zA-Z0-9] [a-zA-Z0-9_+#=:-]*
;
</code></pre>

<p>separate from termination</p>

<pre><code>game_termination
 : WHITE_WINS
 | BLACK_WINS
 | DRAWN_GAME
 | ASTERISK
 ;
</code></pre>
 924: <p>You are right, the text as written there isn't exactly correct.</p>

<p>It also says that the marker is a symbol and lists <code>*</code> as one of the options, even though <code>*</code> is a token on its own and also cannot occur in a symbol.</p>

<p>That said, the meaning is clear enough, 1/2-1/2 is a valid termination marker. How you solve this in your code is up to you. As it's hard to add <code>1/2-1/2</code> as a token on its own (would need lookahead to disambiguate it from symbol <code>1</code> et cetera), it's probably easiest to add '/' to the possible symbol characters, yes.</p>
