Transgender is the usually accepted term these days, not transsexual, for those reading.

My complaint about Taffy isn't even that she's mentally ill... it's that she's a design and some quirks that Jeph threw together with no attempt to actually make her an interesting character. Brun, who a lot of people don't like (although I do) is a reasonably realistic portrayal of a high functioning autistic person, even if she isn't particularly engaging for most readers. Taffy is... an annoying cut out that I feel is an excuse to use a cute design.

There being more and more characters that people who aren't neurotypical/straight/cis/whatever can relate too is great! There being characters that are 2 dimensional cut-outs to facilitate the use of a cute design and for gags are incredibly annoying.