Has a misclick ever costed you a match/round?

Yes

Multiple times in multiple different game modes. I've yet to do it in RD and AA, but in AR, Arena, and GC I've misclicked at least once and have ended up killing my unit. Soleil being the biggest punching bag out of these mistakes ):.

At some points, yes.

Oh yes definitely lol

The best ones are when you double tap your unit and they end turn without having moved

Too. Many. Time.

Before the double tap option update, it happened plenty, but now I have all those settings off to avoid my clumsy ass constantly messing things up.

Though, I still need to work on my positioning. Recently in Arena, I accidentally moved Eir too far for W!Ephraim to make use of her Guidance and I couldn't reach the enemy H!Myrrh, who promptly exploded Eir as soon as her turn came up.

My phone is getting kind of old, so sometimes it'll take a moment before it does what I tap (in general, not just FEH) so that has really screwed me up in the past.

Yep, but mostly in GC. I was using someone’s Hana (With Armorsmasher) to kill Surtr and I accidentally placed her in the range of Reinhardt. He killed her and that Surtr was very difficult to handle with and all the other foes throwing their selves at me. It didn’t end well..