Microsoft Word is a good tool;. However, one needs to keep in mind that it is just that, a tool.
Tools are good. Humans wouldn't have gotten where they are without tools However, one also needs to know when to put the tool down and go with the flow. Take it from me, I write a LOT. Not so much BDSM, although I do have a few of those up on adultfanfiction.net. (Mostly X-Men fanfiction; I have 20 books on fanfiction.net under the pen name Jaenelle Angelline.)
Microsoft word can get extremely anal about words in a different language; as someone who created an entirely new language for a fantasy book I'm writing, Microsoft Word is a pain in the you-know-where.
My basic rule of thumb when I'm writing BDSM (I have one story where two guys are giving a girl an initiation whipping) is that if the girl is screaming, instead of writing,
"Aaaagggghhhh",
I'll write,
"She gave off a high-pitched cry, which started out low and got gradually louder in volume until her Master slapped a gag on her..."
Which, to my way of thinking, is much more descriptive than the long string of vowels and consonants. Some writers do use onomatopoeia because that's their thing, that's they way they write, but my eyes usually tend to skip over it and continue to the story. (Onomatopoeia, by the way, is what this particular literary device is called.) It's not as if most people who read don't have enough imagination to imagine a girl screaming openmouthed as a whip blisters her ass...