Theyre meant to deliver emphasis on the words so you don't read it all monotone in your head. For example maybe "wow, okay. RUDE" but all bold comes off as being too aggressive. I personally think it enhances the post. Also, if you can't handle them, down vote and move on.
I mean, I know that the bold font is meant to add emphasis, and that's exactly the problem. You can only emphasize so many words in a sentence before it starts to grate on your readers' nerves.
I kinda like it. I completely understand why others wouldn't, but I like getting an insight into how the author would say the sentence. My own natural stress falls very differently to the bold words.
I feel like it's of some import to point out that stuff like that makes writing less accessible for some neurodivergent people. I know I had trouble reading it.