The clause in Meld Into Stone that says "you [...] can cast spells on yourself..." is confusing, because it doesn't say with a range of Self or if the rationale is because you are behind full cover.
Some spells can take origin without clear line of sight. For example, find familiar makes it come into existence within a range of 10 feet. Does Meld Into Stone also disallow touch spells like magic stone that can be delivered via a familiar?
Many DM interpret the Meld Into Stone spell as only meaning self range spells, but an alternative interpretation could mean that the spells are on yourself due to the requirement of needing a clear path to a target. If that isn't required due to a find familiar touch delivery mechanism or a touch spell on yourself or a spell that summons a creature within 10 feet of you that does not require sight, how is one supposed to know which is the correct interpretation?