Helpfile[1] seems to be good:
SUMIFS( Reference R ; Reference R1 ; Criterion C1 [ ; Reference R2 ; Criterion C2 ]... )

I don't see where this tooltip is localized.



[1] https://github.com/apache/openoffice/blob/trunk/main/helpcontent2/source/text/scalc/01/04060106.xhp

Comment by RusselB in topic "[Solved] SUMIFS not working for me"
(link provided in the bug report):

"I've noticed this problem in the tooltip text for a few functions,
but it seems to me that it's always a *IFS function..."

These *IFS functions are: AVERAGEIFS, COUNTIFS, and SUMIFS


1. 
Obviously tooltip (shown in the input line / in the cell) does not employ
the entry in the corresponding AOO Help topic (.xhp file).
Instead it is assembled from entries stored in file "scfuncs.src".

Process of creating the data structure (full information on all functions)
and using it are quite complex. Files of interest i.a.:

- global.cxx
http://openoffice-vm1-he-de.apache.org/xref/trunk/main/sc/source/core/data/global.cxx?r=86e1cf34

- scfuncs.src
http://openoffice-vm1-he-de.apache.org/xref/trunk/main/sc/source/ui/src/scfuncs.src?r=4e5ac204

- formulabase.cxx
http://openoffice-vm1-he-de.apache.org/xref/trunk/main/oox/source/xls/formulabase.cxx?r=39c2db0b

- funcdesc.hxx
http://openoffice-vm1-he-de.apache.org/xref/trunk/main/sc/inc/funcdesc.hxx?r=38d50f7b

- inputhdl.cxx
http://openoffice-vm1-he-de.apache.org/xref/trunk/main/sc/source/ui/app/inputhdl.cxx?r=4d7c9de0



2.
Whether commas are added or not depends on what type of arguments
a particular function has.

A method in the source code - ScFuncDesc::GetParamList() composes the string.

http://openoffice-vm1-he-de.apache.org/xref/trunk/main/sc/source/core/data/global.cxx?r=86e1cf34#1469

Part reponsible for paired variable arguments (PAIRED_VAR_ARGS)

1528        {
1529            sal_uInt16 nFix = nArgCount - PAIRED_VAR_ARGS;
1530            for ( sal_uInt16 nArg = 0; nArg < nFix; nArg++ )
1531            {
1532                if (!pDefArgFlags[nArg].bSuppress)
1533                {
1534                    aSig += *(ppDefArgNames[nArg]);
1535                    aSig.Append(sep);
1536                    aSig.AppendAscii(RTL_CONSTASCII_STRINGPARAM( " " ));
1537                }
1538            }
1539 
1540            aSig += *(ppDefArgNames[nFix]);
1541            aSig += '1';
1542            aSig.AppendAscii(RTL_CONSTASCII_STRINGPARAM( ", " ));
1543            aSig += *(ppDefArgNames[nFix+1]);
1544            aSig += '1';
1545            aSig.Append(sep);
1546            aSig.AppendAscii(RTL_CONSTASCII_STRINGPARAM( " " ));
1547            aSig += *(ppDefArgNames[nFix]);
1548            aSig += '2';
1549            aSig.AppendAscii(RTL_CONSTASCII_STRINGPARAM( ", " ));
1550            aSig += *(ppDefArgNames[nFix+1]);
1551            aSig += '2';
1552            aSig.Append(sep);
1553            aSig.AppendAscii(RTL_CONSTASCII_STRINGPARAM( " ... " ));
1554        }


Notice that the code in Line 1542 and 1549 adds _a comma sign_ to the string.

Let's take - as an example - SUMIFS functions. Relevant information is
in file "scfuncs.src".

http://openoffice-vm1-he-de.apache.org/xref/trunk/main/sc/source/ui/src/scfuncs.src?r=4e5ac204#2936


Resource SC_OPCODE_SUM_IFS

Extra Data:             PAIRED_VAR_ARGS+1
Name of Parameter 1:	"sum_range"
Name of Parameter 2:    "range "
Name of Parameter 3:    "criteria "

Parameter 1 is fixed. Parameters 2 and 3 are paired variables.
Therefore the code produces:

"sum_range; range 1, criteria 1; range 2, criteria 2; ..."



3.
As pointed out in the bug report:
"tooltip for SUMIFS contains commas in the syntax which should be semicolons".
The same holds true for any *IFS functions.
The proper sign - a semicolon - one can see in AOO Help, in sections:
"Syntax" and "Example" (cf. the attached file "IFs.jpeg").



4.
Issue confirmed in AOO 4.1.8 and AOO 4.2.-dev



5.
Help vs User Interface
Compare, for example:

AOO Help:
SUMIFS( Reference R ; Reference R1 ; Criterion C1 [ ; Reference R2 ; Criterion C2 ]... )

User Interface:
SUMIFS(► sum_range; range 1, criteria 1; range 2, criteria 2; ... )   

Lack of uniformity in the naming convention is evident.



6.
The Unicode character used in the tooltip i.e. ► 
is BLACK RIGHT-POINTING POINTER, code U+25BA.
Query with search term "0x25ba"

http://openoffice-vm1-he-de.apache.org/search?project=trunk&full=0x25ba&defs=&refs=&path=&hist=&type=&si=full

yields 3 results. Of interest is file:
/trunk/main/sc/source/ui/app/inputhdl.cxx
(cf. point 1. above)



7.
Pootle:
string identifier has one of the prefixes: 
RID_SC_FUNCTION_DESCRIPTIONS1 or RID_SC_FUNCTION_DESCRIPTIONS2
and internal code of function

for example,


SUMIFS function:

"sum_range" ---> scfuncs.src#RID_SC_FUNCTION_DESCRIPTIONS1.SC_OPCODE_SUM_IFS.2.string.text

https://translate.apache.org/pl/translate/#search=scfuncs.src%23RID_SC_FUNCTION_DESCRIPTIONS1.SC_OPCODE_SUM_IFS.2.string.text&sfields=locations


XOR function:

"Number 1" ---> scfuncs.src#RID_SC_FUNCTION_DESCRIPTIONS2.SC_OPCODE_BITXOR.2.string.text
https://translate.apache.org/pl/translate/#search=scfuncs.src%23RID_SC_FUNCTION_DESCRIPTIONS2.SC_OPCODE_BITXOR.2.string.text&sfields=locations



8.
Entries in file "scfuncs.src" are also used in:
- the Function Wizard ('Insert > Function')
- the Function List ('Insert > Functions' or via the Sidebar).




FINAL NOTE (lbl):
I don't know C++ so I might be utterly wrong.

Created attachment 86994 [details]
Screenshots for functions: AVERAGEIFS, COUNTIFS, SUMIFS