Oh I didn't realise it did that! I assumed I'd copied and pasted incorrectly when I submitted it and added the "How" back after the fact.
You can edit it back in after submission.
Yes, true. I've noticed, though, that more often than not HN's deletion of "How"/"Why" makes the title better when it comes to my submissions. I'd estimate 95% of the time I let the HN-auto-edited version stand.