I never liked to wear clothes with any kind of message or insignia on them, either before or after I was diagnosed. As the previous posts (and threads on this subject) have demonstrated, just because a symbol has been designed with a certain meaning in mind, it doesn't guarantee that it will always be interpreted that way. As someone who once worked designing icons for computer applications, I find it hard to imagine that there is any graphic which could unambiguously be read as representing the concept of autism. The diversity of views amongst autistic people about autism also seems to rule out a unanimously agreed "defining feature" of autism which could be used as a visual metaphor. So, whatever symbol is chosen, at best, it's meaning will only be known by the select few who have some incentive to know, especially in a world where we are surrounded all day by a multitude of icons and logos.
Mostly, though, I just don't get the need for a symbol at all. I don't blurt out that I'm autistic to every random stranger I meet, so I don't see the need to advertise the fact on my clothes. If people want to treat us more considerately, then they can just do that, and shouldn't need to be encouraged by having a virtue signal to pin to their lapel. If I have a message to get across, I'll use words; they're not perfect, but much more effective than a graphic that hardly anyone recognises and no-one can agree on the meaning of.
_________________
When you are fighting an invisible monster, first throw a bucket of paint over it.