Oh boy morphology!
This OP shows the limitations of the suffix /-ian/. Technician, logician, statistician, rhetorician, and musician are the simplest of the nine given words. This class of words involves two parts: first, a noun which ends in a hard [k] sound ("technique", "logic", "statistic", "rhetoric", "music"), and the suffix /-ian/ (which turns our hard [k] into a soft [s], important later). Therefore we can hypothesize that /-ian/ can attach to nouns that end in a hard [k] sound.
Mathematician and electrician are similar to the above, except that the words /mathematic/ and /electric/ are not nouns: they are adjectives. The most obvious answer then is that /-ian/ can apply to adjectives as well as nouns.
However, this would mean that our word "economician" should be valid, since it would be /economic/ + /-ian/. (Of course this could just be an exception, but there is a better solution.) The nouns relating to "mathematic", "electric", and "economic" are "mathematics", "electricity", and "economy". With a careful eye, we might note that /economy/ is its own root, but the words "mathematics" and "electricity" themselves are composed of multiple parts!
Mathematics is /mathematic/ + /-s/ (cf words like linguistics, statistics). Electricity is /electric/ + /-ity/ (cf pure/purity, sane/sanity). So what actually happens is that our suffix /-ian/ attaches to roots, not words. Therefore we can have /mathematic/ + /-ian/ and /electric/ + /-ian/, but not /economy/ + /-ian/, because /economy/ doesn't end in a hard [k] sound.
Now, according to my lecture, we should be able to reverse-engineer the word mortician into two parts: /mortic/ and /-ian/. However, /mortic/ as a root doesn't exist in any other word. Therefore, I propose that /mortician/ is its own word, without the /-ian/ suffix. (In fact, its etymology shows that it only ends in "-ian" to match the rest of the words.)
There's a satirical book out there called P is for Pterodactyl. It has a ton of these words, plus some other strange ones. Examples: P is for Pterodactyl, T is for Tsunami, K is for Knight, M is for Mnemonic, C is for Czar.
Individual mobile apps might fail at recognizing Markdown, which reflects very poorly on the devs. Reddit uses Markdown to format text, and this ought to be uniform across all platforms. I use Relay for reddit and it handles Markdown just fine.