Used Linux Fedora 7 

Reproduction
- Open BASIC IDE for My Macros
- Delete sub main (select all, cut)
- Copy the small macro (see below) from this browser window
- Insert the clipboard content into the BASIC IDE
-> The inserted text exceeds the maximum length of this text field...

There is no problem pasting the content to gedit or any other application

Note that the sub below is copied from issue 73457

Sub Main
for i = 1 to 100000: X(a,b): Next i
End Sub
Sub X(n,m)
'X=0 or even a=X
End Sub