Backticked identifiers starting with a number do not show up in REPL tab completions

[harpocrates]

Scala version: all versions of 2.12 and 2.13 I tried, notably 2.12.17 and 2.13.15 (and 2.12.x and 2.13.x at time of opening).

scala> object Test {
     |   def `1 world` = ""
     |   def `one world` = ""
     | }
object Test

scala> Test.
!=(           (universal)   asInstanceOf  (universal)   getClass()    (universal)   notifyAll()   (universal)   →(           (deprecated)
##            (universal)   ensuring(     (universal)   hashCode()    (universal)   one world
+(           (deprecated)   eq(           (universal)   isInstanceOf  (universal)   synchronized( (universal)
->(           (universal)   equals(       (universal)   ne(           (universal)   toString()    (universal)
==(           (universal)   formatted(   (deprecated)   notify()      (universal)   wait(         (universal)

Problem

Although one world shows up in completions, 1 world does not. I ran across this indirectly through Metals, where these presentation compiler completions are also missing.

[harpocrates]

This is fine in Scala 3:

scala> object Test {
     |   def `1 world` = ""
     |   def `one world` = ""
     | }
// defined object Test
                                                                                                                                                                    
scala> Test.
!=             ->             1 world        asInstanceOf   eq             formatted      hashCode       ne             notify         synchronized   wait
##             ==             one world      ensuring       equals         getClass       isInstanceOf   nn             notifyAll      toString       →