who decided it would be a good idea to have THIS and THESE be almost homophones? And that is probably one of my most minor grievances with the damn language.
No one decides things like that. It's just how the language evolved over many centuries. Also, I'm not sure I agree they're almost homophones. The vowels are different,
and the "s" is voiced in one and unvoiced in the other. Native speakers like myself have no trouble distinguishing them. It's pretty much just a problem for some non-native speakers, probably because of difficulty with the different phonology (the vowels in the two are fairly distinct). In any case, there are plenty of other problems with the language that are more fundamental, IMO.
Also why don't you use ¿ To start a question and then ? To end it, seriously is it really worth not writing one character for the cost of not knowing when the stupid question actually starts? Or is there an actual reasoning behind not using ¿ Hell Spanish uses ¿ And ? And in Spanish there are accents that modify words when they are part of a question.
You could ask this question of
almost every language other than Spanish. A better question would be, why do Spanish and a handful of others influenced by it have such a thing, when most others get along just fine without it? Seriously, I can almost always tell when a question is starting, just by the wording. Yeah, there are questions worded like statements (with a meaning like, "It sounds to me like [thing I want to confirm]. Is this true?"), but they aren't really a problem, as long as I can see there's a question mark on the end, which is usually the case.