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If it makes you feel better it's not widely used: https://books.google.com/ngrams/graph?content=regardless%2Cirregardless&year_start=1880&year_end=2019&corpus=

• Emma_Goldman 6y ago
  It's scarcely surprising that it's not used in print. Books are considered, written by those most proficient in English, read and re-read, and professionally proof-read. The extent of its use in ordinary conversation is something else entirely.