By default the RTE in TYPO3 creates and tags which have no semantic meaning but just represent a visual style. Therefore these tags are considered deprecated in modern web design, just like the font-tag. People use CSS to decide if something should be bold or italic. Therefore web developers have switched to strong and em tags which do have a semantic meaning.
Put the following in your TS Setup to convert and tags to and useCss = 0

Program1:

lib.parseFunc_RTE.tags{
  b=TEXT
  b{
    current=1
    wrap= |
  }
  i=TEXT
  i{
    current=1
    wrap= |
  }
}

Program2:

RTE.default {
proc {
entryHTMLparser_db = 1
entryHTMLparser_db {
tags {
// b und i Tags werden ersetzt (em / strong)
b.remap = strong
i.remap = em
}
}
exitHTMLparser_db = 1
exitHTMLparser_db {
tags.b.remap = strong
tags.i.remap = em
}
}
}
RTE.default.FE < RTE.default
RTE.default.useCSS = 0