I've always been of the opinion that Merlin didn't try to use magic to kill Arthur because Morgana didn't know about the magic - but I never really considered that Merlin (or Merlin's magic) was probably actively fighting against the assassination schemes that Merlin did try. I like that interpretation. Especially since you're quite right that, at least with the sword, there was no reason for Merlin to be THAT clumsy in the situation.
It didn't really bother me that Gwen didn't want to tell Arthur. Maybe it didn't make sense, but I think by that point everyone was just so used to hiding EVERYTHING magical from the Pendragons that it was just instinct. But, I can see your point too... and yeah, it was probably so that the writers could keep Merlin as the one person who had never under any circumstances betrayed/hurt Arthur.
Re: Part 2 II
I've always been of the opinion that Merlin didn't try to use magic to kill Arthur because Morgana didn't know about the magic - but I never really considered that Merlin (or Merlin's magic) was probably actively fighting against the assassination schemes that Merlin did try. I like that interpretation. Especially since you're quite right that, at least with the sword, there was no reason for Merlin to be THAT clumsy in the situation.
It didn't really bother me that Gwen didn't want to tell Arthur. Maybe it didn't make sense, but I think by that point everyone was just so used to hiding EVERYTHING magical from the Pendragons that it was just instinct. But, I can see your point too... and yeah, it was probably so that the writers could keep Merlin as the one person who had never under any circumstances betrayed/hurt Arthur.