When I came across Otter at first, I thought same, but then actually read the things you put down. The similarities are pretty easy to see without the creator goggles and the desire all creators have when their work is compared to some other media, all to break that cycle so they can stand on their own and not be called a "ripoff" by some jerk.

I agree that Otter is his own person, and this is a nice comic showing it. All I can say is try to not hold the grudge, let it go and relax, maybe jokingly add it into his character that people assume he is Mae or related to her or something. The messages will never stop, and getting upset at them will just bring you great misery and cause you to lash out like you say this has done with you and NitW, or worse case, grow to resent and hate Otter, and try to lash out and either abandon him, or try so hard to make him so unlike Mae, you could accidentally destroy him.

thank you,
when i look at them even as a creator i am able to see the similarities. its just an easy character design to have be similar.
black (russian blue? for otter) cats that have a chromatic black/grey as their fur, red eyes, and i actually dont know if mae has a tail or not.. i tried seeing references when i drew this and it seems people either draw her with or without one, maybe its implied?

but thank you for seeing both sides of it. he is my child and i will certainly luv him always. maybe one day i wont be so turned off to the game and ill actually play it; i hear its pretty great

It is a really great game, a bit of an emotional rollercoaster, I for sure say you should try it out sometime as it's a good game, but I know the frustration all too well on some level, like how at a point I really hated Undertail because of people trying to push me on playing it and seeing content everywhere and people spoiling parts of the game for me.

Also yeah, totally, Russian Blues have that look to them, as for Mae and her tail, the game mostly just makes it so no one has a tail, like just evolved away the tail as humans did, but their heads still is that of an animal and stuff. I think it's implied, or at least in terms of furries, the tail is drawn often, but in game, no one has a tail as far as I have seen.