Ten months ago, UFO:AI would crash when an underscore was the first character typed into any textbox. It was because text typed into a textbox was being passed to function CL_Translate on every keystroke, in combination with some buffer overflows and/or off-by-one errors. CL_Translate performs text translation and conversion of message ids to plain text.

Most of the issues were worked around in these patches and a few others:
https://github.com/ufoai/ufoai/compare/4c582613df5a...061523ffefb6

However, there remain some more issues, although the game probably won't crash because of them. Attached are some screenshots of the Employees screen.

'''Screenshot 1''': Leading underscores seem to get truncated, but it's really because of gettext lookup.

'''Screenshot 2''': Text with leading underscores CAN still get translated. This should only occur if a particularly short string is being translated by the game, or a user has a peculiar taste in names. In this screenshot, the text has been translated into French.

'''Screenshot 3''': Message IDs can get converted to text. Note how the multi-line text spills over into the area below the textbox. Admittedly, this can't be anything but deliberate, and anybody who does this deserves what they get.

(At one point, I thought that names that converted to text that was too long couldn't be changed, but they can. The cursor just isn't visible at first. Hit the backspace key to make the key invalid, and the cursor will reappear.)

I would suggest that editable textboxes not perform translation / conversion on their contents. The only time it should occur is when the textboxes are initialized with canned text. For example, the initial suggestion for the starting base's name is "Home" in English and "Base Principale" in French.
If this were done, a lone underscore could be considered a proper name again by the function Com_IsValidName, if desired.