Is it considered acceptable to abort a game when...

...the person with the white pieces is deciding on a first move? Surely it is okay to let some of the free seconds elapse while making up one's mind? I'm just wondering. I'm trying very hard not to be a jerk about it. Maybe the other player had an emergency and had no choice but to abort the game...

Why would there be any need for black to abort?
If neither player does anything, white forfeits the game and black is out of it cleanly.

By the way, the countdown towards forfeit, along with the automatic pause after an arena first-move-miss if either side misses their first move are possibly literally there so that a manual abort and manual pause is just unnecessary if manual control is impossible in some situations. If manual control were possible it should obviously be used.

@fin34601473braunpaul My opponent aborted the game while I was using my time to consider my first move...I still had 10 or more seconds to move and I was just about to move my Queen's pawn when he/she aborted the frickin' game. I had not exceeded any time limits.

By the way, my opponent was higher-rated, so I wanted to choose cautiously my first move. Again, I didn't run out of time.

@DoomedBishop

I guess the following: You, white, countdown for your first move ticking, black aborted.
Do you know if your opponent was auto-warned about it?
If yes the server registered something about it of course and it will possibly be sorted out automatically if it happens often.

By the way, of course the server did register something, so it might be best to just move on.
"[colour] left the game" is obviously not acceptable if done intentionally but it can still happen from technical failures.

My opponent was warned about it. I guess I find it irritating for a player to abort the game at all, unless it is an emergency. The person didn't even say anything to me, which is okay if there are consequences. I've had too many people abort games. I don't cheat, I don't taunt players, and I don't mind playing people (and losing) who are rated below me. Maybe I am too angry to see straight...

By the way, this person had left an open challenge for anyone within a certain range. I found the game in the lobby.

My opponent was warned about it.

Good, this means it is in the books.
Pun intended: Move on. :-)

@DoomedBishop said ^

...the person with the white pieces is deciding on a first move? Surely it is okay to let some of the free seconds elapse while making up one's mind? I'm just wondering. I'm trying very hard not to be a jerk about it. Maybe the other player had an emergency and had no choice but to abort the game...

Yes, it is okay to do so!
(But depending the player you’re facing, they might get impatient.)

I once resigned during the game to pick up the package that my brother ordered (my brother was not at home at that time).

I also once aborted the game because my phone’s battery was very low.

some people find it dubious when opponents take time to make first move