1. 在选项设置中把关于 Mathematica 的三个关键替换词 MMA, Mma, mma 给注释掉或删除掉就行了,具体设置见下图 (版本 9 测试有效,其他版本应该也是有效的)

2. 或者直接在当前笔记本界面执行以下代码即可 (PS:执行完之后可以删除),注意代码中的注释部分,此外你也可以添加自定义的关键词
SetOptions[EvaluationNotebook[],
StyleDefinitions ->
Notebook[{Cell[StyleData[StyleDefinitions -> "Default.nb"]],
Cell[StyleData["Text"], InputAutoReplacements -> {"TeX" -> FormBox[
StyleBox[
RowBox[{"T",
AdjustmentBox["E", BoxMargins -> {{-0.3, 0}, {0, 0}},
BoxBaselineShift -> 0.5], "X"}],
SingleLetterItalics -> False], TraditionalForm],
"LaTeX" -> FormBox[
StyleBox[
RowBox[{"L",
StyleBox[
AdjustmentBox["A", BoxMargins -> {{-0.5, -0.3}, {0, 0}},
BoxBaselineShift -> -0.4],
FontSize -> Smaller], "T",
AdjustmentBox["E", BoxMargins -> {{-0.3, 0}, {0, 0}},
BoxBaselineShift -> 0.5], "X"}],
SingleLetterItalics -> False],
TraditionalForm], (*"mma" -> "Mathematica", "Mma" ->
"Mathematica", "MMA" -> "Mathematica",*)
"gridMathematica" -> FormBox[
RowBox[{"grid",
AdjustmentBox[
StyleBox["Mathematica", FontSlant -> "Italic"],
BoxMargins -> {{-0.175, 0}, {0, 0}}]}],
TextForm], "webMathematica" -> FormBox[
RowBox[{"web",
AdjustmentBox[
StyleBox["Mathematica", FontSlant -> "Italic"],
BoxMargins -> {{-0.175, 0}, {0, 0}}]}],
TextForm], ParentList}]},
StyleDefinitions -> "PrivateStylesheetFormatting.nb"]]
若要恢复原来的设置,将上面代码中的注释符去掉,重新执行一下即可,或者新建笔记本或者重启 Mma 也行,或者也可以在上图的设置中添加上原来的关键替换词。
PS:PrivateStylesheetFormatting.nb 这个只是临时性的,只对执行该代码的当前笔记本有效,重启 Mma 或新建笔记本,默认样式定义一般上都不会是这个样式表,所以不会生效,若要永久生效,需要自己定义一个样式表,然后添加下面的语句,在 init.m 中指定默认样式表为该样式表即可。
Cell[StyleData["Text"],
InputAutoReplacements->{"TeX" -> FormBox[
StyleBox[
RowBox[{"T",
AdjustmentBox[
"E", BoxMargins -> {{-0.3, 0}, {0, 0}}, BoxBaselineShift -> 0.5], "X"}],
SingleLetterItalics -> False], TraditionalForm], "LaTeX" -> FormBox[
StyleBox[
RowBox[{"L",
StyleBox[
AdjustmentBox[
"A", BoxMargins -> {{-0.5, -0.3}, {0, 0}}, BoxBaselineShift -> -0.4],
FontSize -> Smaller], "T",
AdjustmentBox[
"E", BoxMargins -> {{-0.3, 0}, {0, 0}}, BoxBaselineShift -> 0.5], "X"}],
SingleLetterItalics -> False], TraditionalForm], "gridMathematica" ->
FormBox[
RowBox[{"grid",
AdjustmentBox[
StyleBox["Mathematica", FontSlant -> "Italic"],
BoxMargins -> {{-0.175, 0}, {0, 0}}]}], TextForm], "webMathematica" ->
FormBox[
RowBox[{"web",
AdjustmentBox[
StyleBox["Mathematica", FontSlant -> "Italic"],
BoxMargins -> {{-0.175, 0}, {0, 0}}]}], TextForm], ParentList}]