I prefer to solve the problem in the right place.

Raw concatenation of bytes without encoding-awareness introduces the possibility that the bytes will combine in unexpected ways. The presence of something as obvious as a BOM makes it harder to make this mistake, at least during the transition phase to "UTF-8 everywhere".

What you really want in this situation is something that forces you to see the potential bug and introduce the correct translation and/or text-concatenation tools to fix it.

And yes, at some point in the future enough tools will be truly aware of UTF-8 that the BOM will not have a reason to exist. But right now it has some value.

So, first you argue that UTF-8 without BOM might split glyphs at incorrect places, and then it's pointed out that UTF-8 with BOM concatenates files incorrectly, and somehow this is also an argument for using BOM?

I'm sorry but it's obvious both approaches have rather symmetrical opportunities to produce bugs. So in that case the best choice seems to be the simplest one. Which is the one without BOM.