Hadn’t noticed but now I gave it a try it’s super annoying.
Making the link above bold is perhaps related to this bug: A Tag Followed by and Underscore Becomes a Header (I totally meant hyphen not underscore. 
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While in that thread I assumed it was related to to tags, but no it’s just anything above a hyphen, and now it breaks if you just do one hyphen. Looks like it’s still a bug in the updated editor.