[css-text-3] Drop questionable characters from space-discarding set for now. Add new open issue.

Author: fantasai

css-text-3/Overview.bs

@@ -5332,18 +5332,12 @@ Space-Discarding Unicode Characters</h2>
     <tr>
       <td>U+31F0..U+31FF
       <td>Katakana Phonetic Extensions
-    <tr>
-      <td>U+3200..U+32FF
-      <td>Enclosed CJK Letters and Months
     <tr>
       <td>U+3300..U+33FF
       <td>CJK Compatibility
     <tr>
       <td>U+3400..U+4DBF
       <td>CJK Unified Ideographs Extension A
-    <tr>
-      <td>U+4DC0..U+4DFF
-      <td>Yijing Hexagram Symbols
     <tr>
       <td>U+4E00..U+9FFF
       <td>CJK Unified Ideographs
@@ -5377,15 +5371,6 @@ Space-Discarding Unicode Characters</h2>
     <tr>
       <td>U+1B130..U+1B16F
       <td>Small Kana Extension
-    <tr>
-      <td>U+1D300..U+1D35F
-      <td>Tai Xuan Jing Symbols
-    <tr>
-      <td>U+1D360..U+1D37F
-      <td>Counting Rod Numerals
-    <tr>
-      <td>U+1F200..U+1F2FF
-      <td>Enclosed Ideographic Supplement
     <tr>
       <td>U+20000..U+2A6DF
       <td>CJK Unified Ideographs Extension B
@@ -5413,6 +5398,8 @@ Space-Discarding Unicode Characters</h2>
 
   ISSUE(4993): Do we include symbol sets like Yijing Hexagrams / Counting Rods / etc.?
 
+  ISSUE(5017): Should we classify symbols as a category of space-ambiguous characters? (Currently spaces are discarded only if both sides are space-discarding; ambiguous characters would discard if the other side is space-discarding.)
+
   For future revisions of [[UNICODE]],
   any new block whose contents comprise at least 50% codepoints belonging to the
   Han, Hiragana, Katakana, or Yi script