If the flotilla keyword is cancelled, can it still shoot through itself?
Yes. The body of a ship (including oars, turtle panels, outriggers, and the little flag at the back) never blocks its own lines of fire. Only a ship’s masts will block its own shots.
Asking for a friend: do derelicts block lines of fire?
Yes. Ships always block lines of fire for other ships, regardless of their condition, unless something else (ability, etc.) specifically says they don’t.
On dismasted ships with Oarsman: are there undesirable outcomes that are avoided by not letting these ships ram other ships? This has come up frequently this year, where a player feels they should be able to ram and board with a ship that has an oarsman.
That’s one of the concessions to “realism” in the game, because a ship limping along with oars isn’t going to be fast enough or maneuverable enough to catch another ship, much less hit it hard enough to actually ram it.
I also always got the impression that oarsmen were originally meant only as a method to maybe save a ship that was severely damaged, while the numerous other uses players have come up with for them over the years were unintended and/or unexpected. Making them also prevent towing was a much later addition/modification of the ability.