I was reading an article about Idlib and the groups that were there on Wikipedia, and hovered to the language setting to gloss at the title translations. For Japanese, I saw something unusual in its format. For example, the rendering of the name of one of those groups is 「タハリール・アル＝シャーム」instead of the usual 「タハリール・アル・シャーム」. I also saw this in manga character names such as「キルシュ＝ワイミー」. Is using the equals sign in place of nakaguro common and is it acceptable? If so, is it solely at the author's discretion?
Technically speaking, this character should be
゠ (U+30A0 KATAKANA-HIRAGANA DOUBLE HYPHEN), not
＝ (U+FF1D FULLWIDTH EQUALS SIGN), and is indeed used to avoid confusion with 長音符:
ー (U+30FC KATAKANA-HIRAGANA PROLONGED SOUND MARK).
From the Double hyphen Wikipedia page:
In Japanese, the double hyphen (ダブルハイフン daburu haifun) in rare cases replaces an English en dash or hyphen when writing foreign words in katakana due to their potential confusion with the prolonged sound mark (ー). It may be used to separate a person's given and family names, such as transcribing the name of Galileo Galilei as: ガリレオ＝ガリレイ. The middle dot (・) is however much more commonly used for these purposes. (For foreign names that include both spaces and hyphens, both the middle dot and double hyphen may appear together as in Catherine Zeta-Jones: キャサリン・ゼタ゠ジョーンズ.) The double hyphen is part of the JIS X 0213 standard, but is not included in more commonly used character encodings, such as Shift-JIS and EUC-JP. For this reason, the equals sign is frequently used in its place.