I can't reproduce this with Mp3tag 3.11 for Windows.
If I use the Convert - Tag-Filename and see at the preview it looks like this:
If I press OK the filename looks like in the preview. The invalid characters for filenames like ? or * are replaced with a space, not a underscore. Update (as @postercorrectly states):
The invalid characters for filenames like ? or * are replaced with nothing, not a underscore.
Can you please show us your preview in Tag - Filename?
I did that already, and you can see the underline. But when I would do that again now, the preview shows the right apostrophe and even after clicking the tag-file name button it worked out this time.
however, i will track the behavior for the next time and will report it here.
Regarding your picture: is it possible to have a rule like when it is a "?" then do nothing (not an extra space).
Hint:
If you want to be sure that only valid characters will be applied to a filename, you can also use: $validate(%artist% - %album% - %track% - %title%,-)
This example replaces all invalid characters /?*"<>|: with dashes.
Apart from the possibilities described here by Lyricslover to influence the behavior of illegal characters for file names or to simply replace characters, the converter of MP3Tag does not write any illegal characters in the file name and e.g. replaces a question mark with "Nothing" like you want.
@poster is right. My first example may be misleading.
This one illustrates how the Convert Tag - Filename handles all non valid characters (for windows: /?*"<>|:) automatically:
first of all, thank you very much for this quick reply. it really helped me.
it is amazing to see forums and communities like this where people help each other - in such a speed - and truly creates value + reduces headache from endless ongoing google searches.