How long can I technically make a ligature before I get an error message, or it begins to cause technical issues? Prior to Glyphs 3 the answer appeared to be 31 letters long, but trying it now I was able to export one that is 64 letters without a problem.
It’s not hugely important, but I’m interested in following this thought experiment for however long it takes me. 
I had a quick look and the format should allow much more. But there might be problems in certain implementations. So you need to test a lot with things like this.
I like poking around the edges to see what’s possible, but it’s always a good practice to ask someone more knowledgeable. 
Think twice. You will run into a lot of text reflow issues and app compatibility problems and your users are going to bombard you with support mails.
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