You can use:
=TRIM(REGEXREPLACE(B2,"[W_]+"," "))
Or, include the space in your character class:
=REGEXREPLACE(B2,"[W_ ]+"," "))
Where: W
is short for [^A-Ba-b0-9_]
, so to include the underscore we added it to the character class.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…