Created attachment 159271 [details]
problem example

Thank you for reporting the bug. I can confirm the bug present in

Version: 6.4.0.0.alpha1+ (x86)
Build ID: ec7374ff84c71edfbb30d6e4dc5b486b6df7107f
CPU threads: 2; OS: Windows 6.1 Service Pack 1 Build 7601; UI render: default; VCL: win; 
TinderBox: Win-x86@42, Branch:master, Time: 2019-11-10_21:37:30
Locale: en-US (en_US); UI-Language: en-US
Calc: threaded
	

and in

LibreOffice 3.3.0 
OOO330m19 (Build:6)
tag libreoffice-3.3.0.4

In fact both cells are indeed Tahoma 8 pt.
But when entering cell A22, each character is Verdana 10 pt.

Extraction the ods file to retrieve content.xml, I see this:
          <table:table-cell table:style-name="ce29" office:value-type="string" calcext:value-type="string">
            <text:p>
              <text:span text:style-name="T1">5</text:span>
              <text:span text:style-name="T2">1</text:span>
            </text:p>
          </table:table-cell>

Here is the definition of ce29:
    <style:style style:name="ce29" style:family="table-cell" style:parent-style-name="Std">
      <style:table-cell-properties style:text-align-source="fix" style:repeat-content="false" />
      <style:paragraph-properties fo:text-align="center" fo:margin-left="0cm" />
      <style:text-properties style:use-window-font-color="true" style:text-outline="false" style:text-line-through-style="none" style:text-line-through-type="none" style:font-name="Tahoma" fo:font-size="8pt" fo:language="none" fo:country="none"
      fo:font-style="normal" fo:text-shadow="none" style:text-underline-style="none" fo:font-weight="normal" style:text-underline-mode="continuous" style:text-overline-mode="continuous" style:text-line-through-mode="continuous"
      style:font-name-asian="Segoe UI" style:font-size-asian="8pt" style:language-asian="none" style:country-asian="none" style:font-style-asian="normal" style:font-weight-asian="normal" style:font-name-complex="Verdana" style:font-size-complex="8pt"
      style:language-complex="none" style:country-complex="none" style:font-style-complex="normal" style:font-weight-complex="normal" style:text-emphasize="none" style:font-relief="none" style:text-overline-style="none"
      style:text-overline-color="font-color" />
    </style:style>

=> Tahoma 8pt

Here are the definitions of T1 and T2:
    <style:style style:name="T1" style:family="text">
      <style:text-properties style:font-name="Verdana" fo:font-size="10pt" style:font-name-complex="Verdana" />
    </style:style>
    <style:style style:name="T2" style:family="text">
      <style:text-properties style:font-name="Verdana" fo:font-size="10pt" style:font-name-complex="Verdana" style:font-size-asian="10pt" style:font-size-complex="10pt" />
    </style:style>

=> Verdana 10 pt

Heiko/Xisco: what should be expected here? font name and font size retrieved from the whole cell and in this case it's correct or should it be blank when the content doesn't correspond? (a bit like when typing a word in Writer, if you change fontname/fontsize just one letter then select the whole word, info are blank).

<18>Hello</18> World  => 10 //cell content partly direct formatted as 18pt
Hello <18>World</18>  => 10
<18>Hello World</18>  => 18 //all cell content direct formatted as 18pt
 <18>Hello World</18> => 10 //white space w/o formatting before
<18>Hello World</18>  => 10 //white space w/o formatting after

The cell content here is <text:span text:style-name="T1">5</text:span><text:span text:style-name="T2">1</text:span> (with T1 <> T2). Sounds like NAB to me.

PS: Ctrl+M clears direct formatting, and View > Value Highlighting helps to identify data mistakenly formatted as text.

Thank you Heiko for the feedback, let's put this one to Not A Bug then.