Hey I'm so glad I found this whole thread. I'm 21 now and have been counting letters in written sentences for a few years now. It's kind of bothering me when I'm watching foreign movies with subtitles. I also count the stairs and my go to number is 16. It has been since I was a kid. When I count letters in my head in french (my first language) it has to add up to an even number. But in english I don't mind it so much I don't know why.
I also have this thing kind of like misophonia but with sudden and loud noises. I get really stressed, sweaty and my heart races when there's a loud noise. For instance one time my fire alarm went off and my heart was racing for at least 20 minutes. I had to stay in complete silence for a while because every little noise scared me. Also just putting down a spoon on a table is hard sometimes because I fear that it's going to make an unbearable noise so I do it very slowly. I think it might be phonophobia but I probably need to see a professional.