Old suggestion should be replaced by new one if author is the same

What happens if someone is not sure about a translation and wants to add another possibility?

I'm not completely sure we should do this...

Then you could discuss this in other forums, with the other translators. I think the goal should be to have one definite suggestion for each string.

Another possibility would be that you're allowed to add additional translations (through a "Add as new suggestion"-checkbox for example) but replacement is the default behaviour. As it is now, there is no way at all to replace your old suggestion, and I think you should be able to.

I agree with Markus. You should be able to add several suggestions, but the default behaviour should be to replace the old one.

Sometimes I find I entered and incorrect translation and, when I change it, the old one still appears as a suggestion... and that would be a mistaken suggestion that could mislead other translators.

When a single suggestion is finally approved, all the others are 'hidden'. I think this is more than enough.

Also, this is a very rare use case (making a mistake and realising it right away), that I'd lean on "won't fix". Carlos? Jeroen?

Ok, Matthew has done a good job of convincing me that this is useful even more than being able to submit two suggestions separately. I refuse to have another field cluttering the UI for something so rarely used, so now we only need to find out which one is going to be the more likely default option, and stick with that.

So there are three ways we could treat someone's suggestion where they've already made a suggestion for that string.
1: Assume they're offering an alternative. If they're correcting their mistake, the old suggestion is something the reviewer can deal with.
2: Assume they're correcting their mistake. If they want to offer an alternative, fix bug 25 so they can discuss it outside the translation field itself.
3: Assume neither, and offer radio buttons or similar for whether they're offering an alternative or a correction.