Knowing when to use jargon in your messaging is about knowing who your audience is, knowing if the context is informal or professional, and then using good judgment. If you know the people well, and it is a personal and informal communication, then absolutely use abbreviation jargon. On the flip side, if you are just starting a friendship or professional relationship with the other person, then it is a good idea to avoid abbreviations until you have developed a relationship rapport.
If the messaging is in a professional context with someone at work, or with a customer or vendor outside your company, then avoid abbreviations altogether. Using full word spellings shows professionalism and courtesy. It is much easier to err on the side of being too professional and then relax your communications over time than doing the inverse.
Capitalize and Punctuate Web/ Texting Abbreviations
Capitalization is a non-concern when using text message abbreviations and chat jargon. You are welcome to use all uppercase (e.g. ROFL) or all lowercase (e.g. rofl), and the meaning is identical. Avoid typing entire sentences in uppercase, though, as that means shouting in online speak.
Proper punctuation is similarly a non-concern with most text message abbreviations. For example, the abbreviation for ‘Too Long, Didn’t Read’ can be abbreviated as TL;DR or as TLDR. Both are an acceptable format, with or without punctuation.
Never use periods (dots) between your jargon letters. It would defeat the purpose of speeding up thumb typing. For example, ROFL would never be spelled R.O.F.L., and TTYL would never be spelled T.T.Y.L.