You know what comes next. The person wrote back, "But they're both equal in Webster 11" (the current abridged).
It's okay to continue to spell "goodbye" with a hyphen, according to these "lexicographers," which nobody does but the people who put the M-W abridged together, yet every mistake is immediately enshrined between the hated red covers.
Book copyeditors have to use this dictionary, just so we'll all be using the same one, and it could be worse.
I agree with you completely, it is so frustrating to see mistakes become accepted usage just through sheer repetition. I grew up in a town, the name of which was two words, and it irritated me over the years to see it gradually combined into one word.