I don´t know, I never had an issue when I typed into the gig description box directly and stayed within the 1200 limit.
Or is your question why the limit is not higher than 1200 characters?
If it´s that, well, my first unconscious reaction to that is Yes, I want more characters, more words! but then when I think about it I´m glad for the limit, because I´d write too much else and buyers might not want to read a whole book on each gig description - the ones who read the descriptions at all probably will read those of more than one seller after all, and those who don´t read them, well, doesn´t matter how short or long the text is in those cases.
Anyway, if you don´t want to write your text so that you have a description at all while waiting for CS to reply, that´s your decision of course.
If it´s a real bug and you can´t even update your gig if you type into the box directly and leave it under 1200 characters, and you did all CS suggested like diligently clearing cache etc., then that´s bad of course, but they told you they refreshed your account already and did escalate it to the tech team and that it may take some time, so I guess you´ll have to wait in that case.
I had a problem with the number of allowed gigs in queue not saving some time ago, and went through the same thing, they refreshed, I cleared etc., nothing helped, but eventually they sorted it out, I think it worked again after 2 days, keep trying to see if the issue is sorted.
I´d not write more than 1 time a day personally, but that´s up to you as well of course.