Indeed, in canon terms, Romulans being keen on suicide is basically an urban myth. In dialogue terms, it's Klingons who are supposed to refuse surrender, and they certainly don't bow too deep to that custom of theirs, either.
On the other hand, we learn from ENT that Romulans love playing with teleoperated ships. They could blow up those left and right if cornered, and this might well lead into a reputation of suicidal tendencies if the enemy didn't suspect the ships were uncrewed.
"The Enterprise Incident" could also be read in this light, with the Romulans operating captured Klingon ships mainly for disinformation purposes. (Heck, perhaps those aren't Klingon ships at all, but Romulan ones with the holo-camouflage turned on, and Kirk gets lucky when beaming into a corridor that really exists where their sensors see it?
)
Timo Saloniemi
On the other hand, we learn from ENT that Romulans love playing with teleoperated ships. They could blow up those left and right if cornered, and this might well lead into a reputation of suicidal tendencies if the enemy didn't suspect the ships were uncrewed.
"The Enterprise Incident" could also be read in this light, with the Romulans operating captured Klingon ships mainly for disinformation purposes. (Heck, perhaps those aren't Klingon ships at all, but Romulan ones with the holo-camouflage turned on, and Kirk gets lucky when beaming into a corridor that really exists where their sensors see it?

Timo Saloniemi