と言(い)ってもいいYou could say, You might say

と is a quoting particle used to mark the content of direct or indirect speech, thoughts, or feelings. For example, 行くと言っていた means '[He] was saying [he] will go.' といってもいい combines と with 言う and the い-Adjective いい, meaning 'You/one could say' (literally, 'It's fine even if one says...').

って est une particule de citation utilisée de manière décontractée pour indiquer un discours direct ou indirect, des pensées, des sentiments, ou pour introduire un sujet de manière informelle. Par exemple, 行くって言っていた signifie « Tu disais que tu (y) irais ». D'un autre côté, といってもいい est utilisé pour exprimer une certaine approximation ou une façon d'exprimer une opinion en disant quelque chose comme « On pourrait dire que... »

The ても form has the core meaning of 'even if.' One common use is Verb + てもいい, which gives or asks for permission—for example, 食べてもいいですか？ literally means 'Is it okay even if I eat this?' but works like 'Can/May I eat this?' in English. Similarly, といってもいい means 'It's okay even if you say...' but is used to express 'You could say' or 'One might say.'

Both と言える and といってもいい can express a meaning similar to the English 'it can/might be said that (A)' with the difference being the degree of assertiveness. と言える is a firmer statement, literally meaning '(A) can be said.'. In contrast, といってもいい sounds more tentative, implying that it would be fine/acceptable to say the thing in question, but allowing for the possibility that other views/opinions may also be valid.

These forms are similar in that both can make a statement sound less certain, but their nuance differs. ないでもない uses a double negative, literally 'It's not not (A).', to express a somewhat unsure positive, e.g., 分からないでもない ('I kind of understand.', or literally 'It's not that I don't understand.'). といってもいい suggests 'you could say (A)', e.g. 問題ないといってもいい ('You could say there's no problem.').