For the first sentence in the quoted rely above, i beg to differ with your school of thought as a well-structured and composed thread can still be characterized or identified based on the proper used of writing equipment made available by the forum which bold is one of those.
As for the second sentence, to my understanding this isn't a formal platform where everyone expects the discussion and style of writing to be so professional or queen-like. This is an informal forum were every style of writing probably is welcomed but still I'm advocating for those feature to be misused or abused.
Overusing tool will make posts more annoying!
Every tool has a useful feature for very special situations. If people use tool appropriately in context, and at acceptable intensity, don't overuse it, tool will give positive effects in general. In contrast, overusing them will cause adverse effects.
Tools (bold, color, glow, underline, italicization, capitalization) are helpful supplementary things, but they are not must one that writers have to use repeatedly; and overuse should be avoided.
In some high standard English test, like IELTS, writers have to make their essays as succinctly as possible. That is what I wrote as well-structured, and well-composed.
If people don't have to use bold in IELTS test to emphasize their ideas, they don't have to use bold in the forum. It is obviously that they can use bold, but it is not a must thing. I use bold too, in some situations.
The most causes that lead posters to make bold here is they naively think that using bold will help their posts become more interesting, and get more attention from readers. They don't know the fact that if readers see a post which totally in bold, they will ignore it (me too).