An Unpopular Opinion: "lmao" is used too much on the internet.
First, I'd like to start with an analysis, if you will.
L - Laughing - describing a sense of funniness
M My - referring to the self as the consumer of the humour
A Arse - referring to a part of the human anatomy to form a slightly offensive reference reinforcing the laugh reaction
O Off - ^^^
"lmao" is commonly used on the internet and especially forums or chat services to express enjoyment of a joke. In some ways, it is parallel of "lol", meaning "laughing out loud". This is one of the most seen acronyms used across the internet. "lmao" is spelled with an L at the front, which in lowercase appears like a capital I. Therefore, newcomers to the internet may try to pronounce it as "eye-may-oh", where in fact the general consensus is "ell-em-ay-oh" (to pronounce as an acronym) or "yl-may-oh" (to pronounce phonetically).
The fundamental concept that the pronouncing is not clear cut obviously shows that "lol" is the superior (and far more commonly used historically, as "lol" has been searched for consistently since 2004 while "lmao" only became mainstream around 2015, at a significantly lesser volume to "lol") acronym. "lol" is simple, clear-cut and phonetically easy to pronounce. In fact, if I was to write the pronunciation into text, it would be the same thing as the acronym essentially.
Second, the use of "arse". This may not offend a lot of people, but the inclusion of a word that may be rude or inappropriate to say for children in an acronym that may be used in places in the internet where children are. In "lol", no potentially rude words are included and the term is harmless. According to Ofcom, the British broadcasting regulator, "arse" is just as rude as "bloody" or "goddamn" and is considered mild.
In conclusion, "lmao"'s use as a drop-in for "lol" is unacceptable. It should be only used to reflect and react to extremely funny jokes or messages, and should not replace "lol". "lol" is clearly easier to pronounce, more acceptable to children, and and is generally an easier to look at acronym.