User blog comment:Alemagno12/Bracket Function/@comment-223.255.230.33-20150107192824/@comment-10429372-20150208071603

No because &[a][b] has no definition, it collapses like a card house, making the strongest defined expression &[a] = a+1.

If it were fixed, it may reach Chained Arrow Notation Level at Extension 1, and 5-entry BEAF at Extension 4.